Fair Game

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Fair Game

Case 37

1 In what mediastinal compartment is this mass located?

2 The majority of anterior mediastinal masses in adult patients arise in which organ?

3 Name at least three causes of thymic masses.

4 How do the metastatic patterns of invasive thymoma and thymic carcinoma differ?

Answers

Case 37

Thymic Mass (Thymic Carcinoma)

3 Thymoma, thymic hyperplasia, thymolipoma, thymic cyst, thymic carcinoma, and thymic carcinoid.

4 Thymic carcinomas metastasize hematogenously, whereas invasive thymomas typically spread locally within the thoracic cavity (especially along the pleura).

Reference

Nishino M, Ashiku SK, Kocher ON, et al: The thymus: a comprehensive review. Radiographics 26:335-348, 2006.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, pp 346-348.

Comment

The differential diagnosis of this poorly marginated, soft tissue attenuation, anterior mediastinal mass includes a thymic neoplasm, lymphoma, and germ cell neoplasm. Lymphoma is typically associated with lymph node enlargement elsewhere, and germ cell neoplasms such as a mature teratoma frequently have evidence of fat attenuation or calcium.

Thymic epithelial neoplasms, most notably thymoma, account for the majority of anterior mediastinal masses in adult patients. Most thymic neoplasms demonstrate well-defined margins on imaging studies. Two notable exceptions are invasive thymoma and thymic carcinoma. Invasive thymoma refers to a thymoma that has invaded its fibrous capsule. Such lesions tend to spread locally, with invasion of adjacent mediastinal structures, chest wall invasion, and contiguous spread along the pleural surface (usually unilaterally). Thymic carcinoma is a rare thymic neoplasm that may be indistinguishable from an invasive thymoma on imaging studies unless distant metastases are present. Unlike invasive thymoma, a thymic carcinoma tends to metastasize hematogenously.

Case 38

1 What is the differential diagnosis for the subcarinal mass in the first figure?

2 Based on the MRI, what is the most likely diagnosis?

3 Name at least three sites of primary neoplasms that commonly result in metastatic intrathoracic lymphadenopathy.

4 What mediastinal interface is displaced laterally in the first figure?

Answers

Case 38

Subcarinal Lymph Node Enlargement Secondary to Metastatic Disease

1 Subcarinal lymph node enlargement, bronchogenic cyst, and left atrial enlargement.

2 Subcarinal lymph node enlargement.

3 Genitourinary, head and neck, breast, and skin (melanoma).

4 Azygoesophageal interface.

Reference

Müller NL, Silva CI: Normal computed tomography of the chest. In: Müller NL, Silva CI, Eds. Imaging of the Chest. Philadelphia, Saunders, 2008, pp 68-72.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, pp 352-353, 373-375.

Comment

The chest radiograph reveals a subcarinal mass, with associated lateral convex bulging of the azygoesophageal interface. The differential diagnosis of a subcarinal mass includes subcarinal lymph node enlargement, bronchogenic cyst, and left atrial enlargement. The MRI reveals that the mass is not vascular and has intermediate signal intensity similar to that of skeletal muscle. The MR features are thus most suggestive of lymph node enlargement. In this patient, the enlarged nodes were secondary to metastatic disease from a primary renal cell carcinoma.

Enlarged mediastinal lymph nodes may be encountered in a wide variety of neoplastic, infectious, and inflammatory conditions. Neoplastic causes include metastatic disease (from bronchogenic carcinoma or an extrathoracic primary), lymphoma, and leukemia. Infectious causes include tuberculosis (TB), fungal, viral, and bacterial infections. Although lymph node enlargement may be evident on CT images in the latter two entities, it is not usually evident on conventional radiographs. Inflammatory causes include sarcoidosis, Castleman’s disease, and angioimmunoblastic lymphadenopathy.

Case 39

1 What term is used to describe the confluent areas of lung opacification observed in these two patients?

2 What pneumoconiosis is associated with this finding?

3 Is this finding typical of the simple or the complicated form of this pneumoconiosis?

4 What term is used to describe the calcification pattern of the lymph nodes in the first figure?

Answers

Case 39

Silicosis

1 Progressive massive fibrosis.

4 Eggshell calcification.

Reference

Chong S, Lee KS, Chung MJ, et al: Pneumoconiosis: comparison of imaging and pathologic findings. Radiographics 26:59-77, 2006.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, pp 201-205.

Comment

Silicosis is a fibrotic lung disease related to the inhalation of dust containing either free crystalline silica or silicon dioxide. Occupational settings related to silica exposure include heavy metal mining, sandblasting, foundry work, and stone masonry. Silicosis is usually a slowly progressive chronic lung disease with a latency period of at least 20 years.

Chronic silicosis is classified into simple and complicated forms. Simple silicosis is asymptomatic and typically presents radiographically with multiple small, nodular opacities, ranging in size from 1 to 10 mm in diameter. The nodules usually have an upper lung zone predominance and frequently calcify. Enlarged nodes are often present and may demonstrate a characteristic peripheral eggshell pattern of calcification, as shown in the first figure.

Complicated silicosis is associated with symptoms and reduced pulmonary function. It is characterized by one or more areas in which silicotic nodules have become confluent, measuring more than 1 cm. Such opacities may be observed in the periphery of the upper lung zone or in the middle lung zone. Over time, these opacities migrate toward the hila, with residual emphysema in the remaining portions of the lungs. In both figures, note the large vertically oriented opacities in the upper and middle lung zones, which are typical of the complicated form of silicosis. As progressive massive fibrosis becomes more extensive, the nodularity in the remaining portions of the lungs usually becomes less apparent.

Case 40

1 What is the distribution of lung abnormalities on these high-resolution CT (HRCT) images?

2 Name at least three causes of chronic infiltrative lung disease that are associated with a basilar and subpleural distribution of abnormalities.

3 Which is more common among patients with progressive systemic sclerosis—nonspecific interstitial pneumonia (NSIP) or usual interstitial pneumonia (UIP)?

4 What soft tissue abnormality might you expect to see in a patient with this diagnosis?

Answers

Case 40

Interstitial Lung Disease Secondary to Progressive Systemic Sclerosis (Scleroderma)

1 Subpleural and basilar.

2 Progressive systemic sclerosis (scleroderma).

Reference

Kim EA, Lee KS, Johkoh T, et al: Interstitial lung diseases associated with collagen vascular diseases: radiologic and histopathologic findings. Radiographics 22:S151-S165, 2002.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, p 220.

Comment

The HRCT images demonstrate a subpleural distribution of irregular linear opacities, ground-glass attenuation, and traction bronchiolectasis. The last term refers to the small, discrete, cystic lucencies in the lung periphery (best demonstrated in the right lower lobe in the first figure [arrows]), which represent dilated bronchioles. A subpleural and basilar predominance of infiltrative lung disease is characteristic of UIP and NSIP.

UIP is characterized histologically by a variegated pattern composed of foci of normal lung, interstitial cellular infiltrates, and intervening zones of active fibrosis and end-stage fibrosis. UIP is associated with a variety of chronic infiltrative lung diseases, including idiopathic pulmonary fibrosis, asbestosis, connective tissue disorders, and drug toxicity. Characteristic HRCT findings in patients with UIP include a subpleural and basilar predominant distribution of irregular linear opacities, ground-glass attenuation, traction bronchiectasis and bronchiolectasis, and honeycombing.

NSIP is characterized by a subpleural and basilar predominant distribution of ground-glass attenuation, irregular linear opacities, and traction bronchiectasis. In contrast to UIP, honeycombing is typically absent in cases of NSIP.

Progressive systemic sclerosis (also referred to as scleroderma), is a connective tissue disorder that is characterized by fibrosis and atrophy of numerous organ systems, including the skin, lungs, gastrointestinal tract, heart, and kidneys. Pulmonary manifestations include interstitial fibrosis, pulmonary vascular disease, and pleural thickening. Other common manifestations include esophageal dilation and dysmotility, enlarged mediastinal lymph nodes, and calcinosis in the skin and subcutaneous tissues.

Case 41

1 What term is used to describe the combination of a calcified lung nodule and calcified lymph nodes?

2 Are these findings more closely associated with primary or reactivation TB?

3 What does the term Ghon focus refer to?

4 Name the two most common radiographic findings associated with primary TB infection.

Answers

Case 41

Ranke Complex

1 Ranke complex.

3 A lung nodule that occurs at the initial site of parenchymal involvement from primary TB.

4 Parenchymal consolidation and mediastinal and hilar lymph node enlargement.

Reference

Burrill J, Williams CJ, Bain G, et al: Tuberculosis: a radiologic review. Radiographics 27:1255-1273, 2007.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, pp 100-102.

Comment

Parenchymal consolidation and mediastinal and hilar lymph node enlargement are the hallmarks of primary TB. The term Ghon lesion (or Ghon focus) refers to a lung nodule that is a residuum of primary TB. In patients with primary TB and an adequate host immune response, the area of lung consolidation slowly regresses to form a well-circumscribed nodule. Such a nodule may disappear altogether or may remain as a solitary calcified granuloma, referred to as a Ghon lesion. Lymph node enlargement, another sign of primary TB infection, also regresses. Residual calcified lymph nodes may be seen, as demonstrated in the aorticopulmonary window and left hilum in this patient.

Case 42

1 What is the most likely cause for the acute interstitial process demonstrated in the second figure?

2 What is the difference between Kerley A lines and Kerley B lines?

3 At approximately what pulmonary venous wedge pressure (PVWP) would you expect to detect Kerley lines?

4 Name at least three radiographic signs of interstitial edema.

Answers

Case 42

Interstitial Edema

1 Interstitial edema.

2 Kerley A lines are centrally located, radiate from the hila, and measure 2 to 6 cm in length; Kerley B lines are peripherally located, usually extend to the pleural surface, and measure less than 2 cm in length.

3 Higher than 17 mm Hg.

4 Peribronchial cuffing, indistinct pulmonary vessels; interlobular septal thickening (Kerley lines), and thickening of the fissures.

Reference

Müller NL, Silva CIS: Interstitial patterns. In: Silva CIS, Müller NL, Eds. Imaging of the Chest. Philadelphia, Saunders, 2008, pp 158-199.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, pp 330-332.

Comment

The chest radiograph in the second figure demonstrates several typical findings of interstitial edema, including indistinctness of the pulmonary vessels, peribronchial cuffing, and thickened septal (Kerley) lines. The presence of a recent normal baseline radiograph (first figure) confirms that this is an acute process. Significant ancillary findings include interval slight increase in heart size and increased caliber of upper lobe vessels (cephalization).

Cardiogenic pulmonary edema refers to excess extravascular fluid within the lungs secondary to increased pulmonary microvascular pressure, which is usually due to diseases of the left side of the heart such as left ventricular failure. Cardiogenic pulmonary edema usually follows a typical course. It begins in the interstitial compartment and extends into the alveolar compartment as it increases in severity.

The characteristic radiographic findings of pulmonary venous hypertension and congestive heart failure have been shown to correlate with physiologic parameters such as the PVWP. Normally, the PVWP is lower than 12 mm Hg. As PVWP rises to between 13 and 17 mm Hg, you should expect to see vascular redistribution. At PVWP higher than 17 mm Hg, Kerley lines are usually visible. At PVWP values higher than 20 mm Hg, a right-sided pleural effusion is often evident. When PVWP rises above 25 mm Hg, you should expect to see airspace opacities, usually most prominent in the central, perihilar regions of the lungs.

The chest radiographic features may lag behind the clinical status of the patient as pulmonary edema resolves. Radiographic findings of pulmonary edema may persist despite a return to normal wedge pressure measurements.

Case 43

1 What airway abnormality is present in this patient?

2 What is the most common cause of this abnormality?

3 What conventional radiographic sign of bronchiectasis is evident in the lung bases in the first figure?

4 Name at least three CT findings associated with bronchiectasis.

Answers

Case 43

Bronchiectasis in a Patient With Marfan’s Syndrome

1 Bronchiectasis.

2 Prior infection.

3 “Tram-tracking” (bronchial wall thickening).

4 Bronchial diameter greater than adjacent arterial diameter, identification of bronchi in the lung periphery, lack of normal bronchial tapering, bronchial wall thickening, and strings or clusters of cysts ± air-fluid levels.

Reference

Javidan-Nejad C, Shall S: Bronchiectasis. Radiol Clin North Am 47:289-306, 2009.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, pp 314-321.

Comment

Bronchiectasis is defined as abnormal, irreversible dilation of the bronchi. Bronchiectasis may arise secondary to a wide variety of congenital and acquired abnormalities. Cystic fibrosis is the most common associated congenital abnormality, and prior infection, especially childhood viral illnesses, is the most common acquired abnormality. Bronchiectasis is a rare complication of Marfan’s syndrome. Note the characteristic elongated thorax of this patient on the lateral radiograph.

Chest radiographs are frequently normal in patients with mild degrees of bronchiectasis but may occasionally reveal parallel thickened bronchial walls, also referred to as a tram-track appearance. With cystic bronchiectasis, radiographs may reveal clusters of air-filled cysts, often with fluid levels. HRCT is highly sensitive and specific for diagnosing bronchiectasis. Findings include a bronchial wall diameter greater than its adjacent artery (resulting in a “signet-ring” sign when the dilated bronchus and accompanying artery are viewed in cross-section), identification of bronchi within the peripheral centimeter of the lung, lack of normal bronchial tapering, bronchial wall thickening, and strings or clusters of cysts. Because bronchial wall thickening may also be seen in other forms or airways disease, it should not be used as a sole criterion for diagnosis bronchiectasis. Complications of bronchiectasis include recurrent infections, hemoptysis, mucoid impaction, and atelectasis (note the left lower lobe atelectasis in the second figure).

Case 44

1 What abnormality is depicted on this image?

2 What syndrome is associated with pulmonary arteriovenous malformations (AVMs)?

3 Approximately what percentage of AVMs are multiple?

4 Name at least three symptoms or conditions that may be associated with a pulmonary AVM.

Answers

Case 44

Arteriovenous Malformation

2 Hereditary hemorrhagic telangiectasia (HHT), also known as Osler-Weber-Rendu disease, which is characterized by telangiectasias, AVMs, and aneurysms in multiple organ systems (including pulmonary, gastrointestinal, cutaneous, and central nervous system).

3 Approximately 30%.

4 Cyanosis, dyspnea, stroke, and brain abscess.

Reference

Lee EY, Boiselle PM, Cleveland RH: Evaluation of congenital lung anomalies. Radiology 247:632-648, 2008.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, pp 75-77.

Comment

An AVM represents an abnormal communication between the pulmonary arteries and veins in which there is absence of the capillary network that normally separates these vascular structures. This process results in a right-to-left shunt. Although many patients are asymptomatic at the time of initial presentation, complications of right-to-left shunting include cyanosis, dyspnea, stroke, and brain abscess.

Pulmonary AVMs have a lower lobe predominance, and they often occur in the medial third of the lung. AVMs are defined as simple when there is a single feeding artery and a single feeding vein; they are complex when there are two or more feeding arteries and two or more draining veins.

On chest radiographs, pulmonary AVMs appear as well-defined nodules, which often have lobulated contours. A feeding artery and draining vein can often be identified.

Pulmonary arteriography was historically the modality of choice for defining the number, size, and angioarchitecture of these lesions. However, multidetector CT (MDCT) angiography with multiplanar reformation and three-dimensional reconstructions has been shown to be equivalent to pulmonary arteriography for detection of AVMs and characterization of their angioarchitecture. MDCT is now the imaging study of choice for screening for pulmonary AVMs and may also be used to help select appropriate therapy. Pulmonary AVMs larger than 2 cm are usually treated with endovascular coil embolization or balloon occlusion.

Case 45

1 In which mediastinal compartment is this mass located?

2 What is the most likely diagnosis for this mass?

3 How would you characterize this aneurysm according to its shape?

4 Is this a typical location for an aneurysm associated with cystic medial necrosis?

Answers

Case 45

Saccular Aortic Aneurysm

2 Aortic aneurysm.

Reference

Agarwal PP, Chughtai A, Matzinger FRK, Kazerooni EA: Multidetector CT of thoracic aortic aneurysms. Radiographics 29:537-552, 2009.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, pp 358-359.

Comment

Vascular abnormalities, including aneurysms and vascular variants, are an important cause of middle mediastinal masses. You should consider the diagnosis of an aortic aneurysm whenever you detect a mass in close proximity to the aorta, particularly if a border of the mass is indistinguishable from the aortic contour. The diagnosis can be confirmed with either contrast-enhanced CT or MRI.

A thoracic aortic aneurysm is an abnormal dilation of the aorta. Aortic aneurysms can be classified according to shape, integrity of the aortic wall, and location. With regard to shape, aneurysms may be classified as either saccular or fusiform. Saccular aneurysms are characterized by a focal outpouching of the aorta, as demonstrated in the second figure. Such aneurysms are often traumatic or infectious in etiology. Fusiform aneurysms, conversely, are characterized by cylindrical dilation of the entire aortic circumference. This configuration is typical of atherosclerotic aneurysms.

Based on the integrity of the aortic wall, aneurysms may be classified as either true or false. True aneurysms have an intact aortic wall. The most common cause of a true aneurysm is an atherosclerotic aneurysm. In contrast, false aneurysms are associated with a disrupted aortic wall. Examples of false aneurysms include infectious (mycotic) and posttraumatic aneurysms.

Regarding location, aneurysms may be classified as involving primarily the ascending aorta, aortic arch, or descending aorta. Aneurysms that classically involve the ascending aorta include those related to cystic medial necrosis and syphilis. Other causes of aneurysms, including atherosclerotic, mycotic, and posttraumatic etiologies, most often affect the descending thoracic aorta and aortic arch.

Case 46

1 What is the differential diagnosis for the wedge-shaped, peripheral consolidation in the left lung in the first figure?

2 What is the significance of the identification of a feeding vessel directed toward the apex of the consolidation?

3 What feature of peripheral consolidations has been described as highly suggestive of pulmonary infarction?

4 What is the estimated prevalence of “incidentally detected” acute pulmonary embolism on contrast-enhanced spiral CT?

Answers

Case 46

Pulmonary Infarction

1 Pulmonary infarct, neoplasm, pneumonia, and hemorrhage.

2 A feeding vessel is a feature that is more typical of pulmonary infarction than the other entities listed in Answer 1.

3 Central lucencies (round foci of hypoattenuation in the central portion of a wedge-shaped opacity).

4 Approximately 1% to 5%.

Reference

Revel MP, Triki R, Chatellier G, et al: Is it possible to recognize pulmonary infarction on multisection CT images? Radiology 244:875-882, 2007.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, p 50.

Comment

Pulmonary infarcts typically appear as wedge-shaped foci of consolidation, with their bases abutting the visceral pleura. Like pulmonary emboli, they are usually multiple, and they typically have a basilar predominance.

Revel and colleagues recently assessed the sensitivity and specificity of four findings (triangular shape, vessel sign, central lucencies, and air bronchograms) for distinguishing pulmonary infarction from other causes of peripheral consolidation. Among these features, central lucencies and a feeding vessel (vessel sign) were more commonly associated with pulmonary infarction, with likelihood ratios of 23 and 2.9, respectively. Thus, when you identify a wedge-shaped peripheral area of consolidation with central lucencies and/or a feeding vessel, you should carefully assess for coexisting pulmonary embolism.

Case 47

1 What is the differential diagnosis of multiple lung nodules or masses in a patient with acquired immunodeficiency syndrome (AIDS)?

2 In AIDS patients, is the doubling time of nodules a reliable way to differentiate between benign and malignant conditions?

3 What is the most common type of lymphoma to affect patients with AIDS?

4 Is thoracic lymphoma typically nodal or extranodal in AIDS patients?

Answers

Case 47

AIDS-Related Lymphoma

1 Infection (fungal, mycobacterial, septic emboli) and neoplasm (lymphoma and Kaposi’s sarcoma).

3 Non-Hodgkin’s lymphoma.

Reference

Boiselle PM, Aviram G, Fishman JE: Update on lung disease in AIDS. Semin Roentgenol 37:54-71, 2002.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, pp 131-133.

Comment

Lymphoma is a common AIDS-related neoplasm, but thoracic involvement is present in only a minority of AIDS patients with non-Hodgkin’s lymphoma. Thoracic lymphoma is usually associated with disseminated disease involving the central nervous system, gastrointestinal tract, and bone marrow. In AIDS patients, thoracic lymphoma is typically extranodal. Thus, abnormalities of the lung parenchyma (nodules, masses, interstitial parenchymal opacities) and pleura (effusions) are encountered more frequently than lymph node enlargement.

The differential diagnosis of multiple nodules or masses includes infections and other neoplasms, especially Kaposi’s sarcoma. In AIDS-related lymphoma, nodules and masses may grow quite rapidly, with doubling times similar to that of infectious nodules. Thus, a rapid doubling time is not a reliable indicator of benignancy in AIDS patients. With regard to Kaposi’s sarcoma, it can be differentiated from lymphoma by its lack of uptake on gallium scans. In contrast, lymphoma is gallium-avid.

Case 48

1 Name the three most common sites of traumatic aortic transection.

2 Of those patients who survive to reach the hospital, what is the most common site of injury?

3 Is a mediastinal hematoma specific for aortic injury?

4 Is aortography commonly used to detect aortic injury?

Answers

Case 48

Traumatic Aortic Transection

1 At the level of the ligamentum arteriosum, the aortic root, and the diaphragm.

2 The level of the ligamentum arteriosum.

Reference

Kaewlai R, Avery LL, Asrani AV, Novelline RA: Multidetector CT of blunt thoracic trauma. Radiographics 28:1555-1570, 2008.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, pp 170-175.

Comment

Acute thoracic aortic injury is a serious complication of blunt chest trauma, with an associated high mortality rate. The majority of affected patients die before reaching the hospital, and approximately half of those who present to the hospital die within 1 week without appropriate treatment.

MDCT plays an important role in screening trauma patients for evidence of mediastinal hematoma, an important indirect sign of aortic injury. Although mediastinal hemorrhage is sensitive for detecting aortic injury, it is not very specific. For example, mediastinal hematoma may be associated with injuries to other arterial and venous structures as well as with nonvascular injuries, such as sternal and spinal fractures. When hemorrhage is localized to the periaortic region (first figure), it is more specific for aortic injury. When you identify hemorrhage, you should look carefully for direct signs of aortic injury.

Direct signs of aortic injury include deformity of the aortic contour (second figure), intimal flap (arrow in the second figure), intraluminal thrombus, pseudoaneurysm, and frank extravasation of contrast. Multiplanar and three-dimensional reconstructions provide important complementary information to axial CT images including distance of injury from aortic arch branch vessels, length of injury, aortic diameter above and below the site of injury, and coexisting vascular anomalies. Precise characterization of the injury is important for guiding treatment decisions, including surgical repair and stent placement.

Case 49

1 What is the most common cause of a thoracic inlet mediastinal mass in an adult patient?

2 What is the most common cause of a thoracic inlet mass in a child?

3 Which CT imaging feature of this mass makes untreated lymphoma a highly unlikely diagnosis?

4 Do thyroid goiters typically enhance with intravenous contrast?

Answers

Case 49

Thyroid Goiter

1 Thyroid goiter.

2 Lymphangioma.

3 The presence of calcification.

Reference

Reed JC: Anterior mediastinal mass. In: Chest Radiology: Plain Film Patterns and Differential Diagnoses, fourth edition. St. Louis, Mosby–Year Book, 1997, pp 107–124.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, pp 351-352.

Comment

A thyroid goiter is the most common cause of a mediastinal mass in the thoracic inlet region in adults. On chest radiographs, a substernal goiter typically presents as a well-defined mass that extends through the thoracic inlet from the neck and is frequently associated with deviation and/or compression of the trachea. On CT imaging, characteristic features include continuity with the cervical thyroid gland, foci of high attenuation on noncontrast images (reflecting the high iodide content of thyroid tissue), focal areas of cysts and calcification, and intense enhancement following intravenous contrast administration.

Although lymphoma may infrequently present as a thoracic inlet mass, calcification is rarely encountered in untreated cases of lymphoma. In contrast, calcification is a common feature of thyroid goiters.

Case 50

1 What is the most likely diagnosis?

2 Name four other causes of chronic airspace consolidation.

3 How can you differentiate this entity from the remaining causes of chronic consolidation?

4 What aspirated substance is most closely associated with this entity?

Answers

Case 50

Lipoid Pneumonia

1 Lipoid pneumonia.

2 Bronchioloalveolar carcinoma (BAC), alveolar proteinosis, lymphoma, and “alveolar” sarcoid (not a true alveolar process).

3 Only lipoid pneumonia is characterized by fat density on CT.

Reference

Rossi SE, Erasmus JJ, Volpacchio M, et al: “Crazy-paving” pattern at thin-section CT of the lungs: radiologic-pathologic overview. Radiographics 23:1509-1519, 2003.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, p 237.

Comment

Exogenous lipoid pneumonia is associated with the inadvertent aspiration of oily substances such as mineral oil. On conventional radiographs, lipoid pneumonia typically appears as chronic alveolar consolidation, which is usually most prominent in the lung bases. Lipoid pneumonia infrequently presents as a focal masslike opacity.

On CT examination, the areas of consolidation are characterized by low density, reflecting their fatty composition. The identification of negative CT density numbers in the range of fatty tissue (e.g., –50 to –150 Hounsfield units) within the consolidation is pathognomonic for lipoid pneumonia. Less characteristically, exogenous lipoid pneumonia may manifest on HRCT as geographic ground-glass attenuation with superimposed smooth septal thickening (“crazy paving” pattern) due to intraalveolar and interstitial accumulation of lipid-laden macrophages and hyperplasia of type II pneumocytes along the alveolar lining.

Affected patients are frequently asymptomatic, but a minority of patients present with chronic symptoms of cough and dyspnea. Such symptoms generally resolve once the patient discontinues using the offending substance.

With regard to the differential diagnosis of chronic alveolar consolidation, you may narrow the differential diagnosis by assessing whether the process is focal or diffuse. Focal areas of chronic consolidation may be seen in lipoid pneumonia, BAC) and lymphoma. Diffuse chronic consolidation can be seen in BAC, alveolar proteinosis, alveolar sarcoid, and lipoid pneumonia. Lipoid pneumonia typically has a dependent distribution, which is not typical of other causes of chronic diffuse alveolar consolidation.

Case 51

1 What is the most likely diagnosis?

2 What is the classic triad of abnormalities associated with this entity?

3 Name one other manifestation that affects male patients with this disorder.

4 What is the pattern of inheritance?

Answers

Case 51

Kartagener’s Syndrome

1 Kartegener’s syndrome.

2 Situs inversus, bronchiectasis, and sinusitis.

4 Autosomal recessive.

Reference

Javidan-Nejad C, Bhalla S: Bronchiectasis. Radiol Clin North Am 47:289-306, 2009.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, pp 319-320.

Comment

Kartagener’s syndrome is a subset of the dyskinetic cilia syndrome, a congenital cause of bronchiectasis that is associated with an autosomal recessive pattern of inheritance. In patients with the dyskinetic cilia syndrome, ciliary function is typically abnormal throughout the body. Thus, affected males are infertile on the basis of immotile sperm.

Patients with Kartagener’s syndrome typically present in childhood with symptoms related to bronchitis, sinusitis, and rhinitis. Bronchiectasis usually develops in childhood and young adulthood, and it is associated with recurrent pneumonias. Bronchiectasis is typically less severe than in cases of cystic fibrosis, another congenital cause of bronchiectasis. Interestingly, in patients with Kartagener’s syndrome, bronchiectasis has a predilection for the anatomic right middle lobe.

On imaging studies, the combination of situs inversus and bronchiectasis suggests the diagnosis. Ancillary findings may include overinflation of the lungs and focal areas of consolidation and atelectasis.

Case 52

1 What is the most likely cause of left upper lobe atelectasis in this patient?

2 Name five tumors that may affect central airways.

3 Based solely on the degree of postobstructive atelectasis present, what is the correct T (tumor) stage for this non–small cell lung cancer (NSCLC)?

4 What is the most likely cell type of lung cancer in this patient?

Answers

Case 52

Left Upper Lobe Collapse Secondary to Lung Cancer

2 Lung cancer, carcinoid, mucoepidermoid carcinoma, hamartoma, endobronchial metastasis.

4 Squamous cell carcinoma.

References

Kligerman S, Abbott G: Revised TNM staging system for nonsmall cell lung cancer. AJR Am J Roentgenol 194:562-573, 2010.

Rami-Porta R, Crowley JJ, Goldstraw P: The revised TNM staging system for lung cancer. Ann Thorac Cardiovasc Surg 15:4-9, 2009.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, pp 31-37, 258-261, 263-266.

Comment

The most common cause of complete lobar atelectasis is obstruction of a central bronchus. In an adult patient, lung cancer is the most likely diagnosis.

The tumor-node-metastases (TNM) system for staging lung cancer was revised in 2009. According to this classification system, a centrally obstructing neoplasm with associated postobstructive atelectasis or obstructive pneumonitis that extends to the hilar region but does not involve the entire lung is classified as T2. If the entire lung is involved, then the primary tumor is classified as T3.

Squamous cell carcinomas typically occur in main, segmental, or subsegmental bronchi and grow endobronchially. In contrast, small cell carcinoma is characterized by a submucosal, peribronchial growth pattern and a discrete endobronchial tumor is seldom identified. Small cell carcinoma typically occurs as a large central mass that may narrow the bronchial lumen by extrinsic compression. Adeoncarcinomas of the lung are typically peripheral tumors.

Case 53

1 What is the most likely diagnosis?

2 What other organ system is frequently involved by this disorder?

3 Does this patient have the “limited” form of this disorder?

4 What laboratory test is most helpful for confirming this diagnosis?

Answers

Case 53

Wegener’s Granulomatosis

1 Wegener’s granulomatosis.

4 Cytoplasmic pattern of antineutrophil cytoplasmic autoantibody (cANCA).

Reference

Ananthakrishnan L, Sherma N, Kanne JP: Wegener’s granulomatosis in the chest: high-resolution CT findings. AJR Am J Roentgenol 192:676-682, 2009.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, p 225.

Comment

Wegener’s granulomatosis is a necrotizing vasculitis that classically involves the upper respiratory tract, lungs, and renal glomeruli. A limited form of the disease is largely confined to the lung and is associated with a better prognosis than the classic form.

The thoracic radiologic manifestations of Wegener’s granulomatosis are varied, but the most characteristic pattern is that of multiple lung nodules or masses. Such nodules and masses are usually round in configuration, with well-defined margins. They range from 1 or 2 mm to 9 cm in diameter, and cavitation is evident in up to one half of cases. On CT scans, the nodules frequently demonstrate angiocentric features, such as the presence of feeding vessels and a peripheral distribution. The second most common pattern is focal or diffuse alveolar consolidation, which corresponds to the presence of pulmonary hemorrhage.

The diagnosis requires consistent pathologic, radiologic, clinical, and laboratory data. The presence of a cytoplasmic pattern of cANCA, as detected by indirect immunofluorescence of serum, is suggestive of the diagnosis. Treatment with a combination of cyclophosphamide and steroids is successful in most cases.

Case 54

1 Which type of infection most commonly presents with multiple poorly defined lung nodules in an immunosuppressed patient?

2 Is the “CT halo sign” (a “halo” of ground-glass opacification surrounding a nodule) specific for Aspergillus?

3 What does the ground glass surrounding the nodule represent?

4 Is the CT halo sign typically seen early or late in the course of infection with Aspergillus?

Answers

Case 54

Invasive Aspergillus

Reference

Franquet T, Müller NL, Giménez A, et al: Spectrum of pulmonary aspergillosis: histologic, clinical and radiologic findings. Radiographics 21:825-837, 2001.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, pp 122-123.

Comment

Invasive pulmonary aspergillosis is the most common fungal infection to affect immunosuppressed patients. It usually affects patients with severe neutropenia, including recent bone marrow transplant recipients, patients with hematologic malignancies, and patients receiving high-dose steroids. Because it is a potentially lethal infection, prompt recognition and treatment are critical.

Aspergillus organisms invade blood vessels, resulting in areas of pulmonary infarction. On chest radiographs, you may observe multiple poorly defined nodular opacities and more confluent areas of consolidation. Foci of consolidation are often wedge-shaped and peripheral in location. When imaged with CT scanning early in the course of infection, the nodules typically demonstrate a halo of ground-glass attenuation, which corresponds to the presence of hemorrhage. In the proper clinical setting (e.g., profound neutropenia), the CT halo sign is highly suggestive of Aspergillus infection. However, it is not specific for Aspergillus, because it may also be seen in association with other infections (mucormycosis), vasculitides, and hemorrhagic metastases. Later in the course of infection, the nodules may undergo cavitation (the “air crescent sign”). Such cavitation occurs after granulocyte recovery and usually indicates a good prognosis.

Case 55

1 Name two infiltrative lung diseases that are associated with a cystic pattern.

2 Describe the typical demographic features (age, sex) of a patient with lymphangioleiomyomatosis (LAM).

3 Is LAM associated with cigarette smoking?

4 Name two pleural complications of LAM.

Answers

Case 55

Lymphangioleiomyomatosis

1 LAM and eosinophilic granuloma.

2 Young (reproductive age) female. Average age at diagnosis is 35 years.

4 Pneumothorax and chylothorax.

Reference

McCormack FX: Lymphangioleiomyomatosis: a clinical update. Chest 133:507-516, 2008.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, pp 195-196.

Comment

LAM is a rare disease that affects women during their reproductive years. Pathologically, it is characterized by abnormal proliferation of immature smooth muscle cells and the presence of thin-walled lung cysts. Such cysts may rupture, leading to spontaneous pneumothoraces. Lymphatic obstruction may result in chylous pleural effusions.

On conventional radiographs, you may observe a diffuse linear pattern, with preserved or increased lung volumes. Pleural abnormalities, including pneumothorax and pleural effusion, may also be evident. The hallmark of LAM on HRCT is the presence of numerous thin-walled cysts, which are usually regular and uniform in configuration. The intervening lung is typically normal.

The main differential diagnosis is Langerhans cell histiocytosis (LCH). In this disorder, cysts are usually accompanied by small nodules, which may undergo cavitation. Unlike the cysts in LAM, LCH-related cysts have a more variable appearance, with occasional bizarre configurations. Finally, LCH typically spares the costophrenic sulci, whereas LAM has a more diffuse distribution.

Current treatments for LAM include progesterone and, less commonly, oophorectomy. Lung transplantation is a viable option for patients with severe disease. Multicenter trials are under way to assess new molecular-based therapeutic agents.

Case 56

1 What is the most likely cause of focal consolidation in a human immunodeficiency virus (HIV)–positive patient?

2 What is the second most common cause?

3 How often does Pneumocystis jiroveci pneumonia (PCP) present with this pattern?

4 Are recurrent bacterial pneumonias an AIDS-defining illness?

Answers

Case 56

Community-Acquired Bacterial Pneumonia

1 Community-acquired bacterial pneumonia.

3 In approximately 10% of cases.

Reference

Boiselle PM, Tocino I, Hooley RJ, et al: Chest radiograph interpretation of Pneumocystis carinii pneumonia, bacterial pneumonia, and pulmonary tuberculosis in HIV-positive patients: accuracy, distinguishing features, and mimics. J Thorac Imaging 12:47-53, 1997.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, pp 128-131.

Comment

The chest radiograph plays an important role in the evaluation of pulmonary infections in HIV-positive patients. Despite some overlapping features among various infections, chest radiograph pattern recognition can help to narrow the differential diagnosis of pulmonary infections in HIV-positive patients.

With regard to a pattern of focal or lobar consolidation, bacterial pneumonia is the most likely etiology. Bacterial pneumonias are especially common early in the course of HIV infection (CD4 greater than 200/mm³), and recurrent bacterial pneumonias are now included as an AIDS-defining illness. Commonly encountered bacterial pathogens include Streptococcus, Haemophilus influenzae, Staphylococcus, and gram-negative organisms.

When focal or lobar consolidation is accompanied by mediastinal and hilar lymph node enlargement, TB should be considered. Other causes of focal or lobar consolidation are less common, including PCP (which more typically presents as diffuse, bilateral parenchymal opacities) and Mycobacterium avium-intracellulare infection.

Case 57

1 What infection is most closely associated with low-density nodes with peripheral enhancement?

2 Is lymph node enlargement more common in primary TB or post-primary TB?

3 In patients with primary TB, is lymph node enlargement more common in pediatric or adult patients?

4 Concerning HIV-positive patients and TB, are enlarged mediastinal lymph nodes encountered more commonly in patients with CD4 counts above 200/mm³ or in patients with CD4 counts below 200/mm³?

Answers

Case 57

Tuberculosis

4 CD4 counts below 200/mm³.

Reference

Burrill J, Williams CJ, Bain G, et al: Tuberculosis: a radiologic review. Radiographics 27:1255-1273, 2007.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, pp 100-102, 353.

Comment

Lymph node enlargement is a characteristic feature of primary TB, particularly in children. Lymph node enlargement may occur alone or in association with parenchymal consolidation. On contrast-enhanced CT scans of patients with mediastinal tuberculous lymphadenitis, enlarged nodes often demonstrate a low-density center and peripheral rim enhancement. Histologically, such nodes have been shown to demonstrate central necrosis and a highly vascular, inflammatory capsular reaction.

Although low-density nodes are characteristic of TB, they are not specific for this entity. Such nodes may also be encountered in atypical mycobacterial and fungal infections. Neoplastic lymph nodes (e.g., metastatic seminoma) may also demonstrate this appearance.

With regard to TB in HIV-positive patients, the radiographic appearance varies depending on the patient’s CD4 count. In patients with CD4 counts above 200/mm³, a post-primary pattern is typically seen. In patients with CD4 counts below 200/mm³, you will usually observe a primary pattern, including low-density lymph nodes and consolidation.

Case 58

1 In an HIV-positive patient, what is the most likely diagnosis for these findings?

2 Is this infection increasing or decreasing in prevalence among HIV-positive patients in the United States?

3 Below what CD4 count level are patients at risk for Pneumocystis pneumonia?

4 Does a normal chest radiograph exclude this infection?

Answers

Case 58

Pneumocystis jiroveci Pneumonia

1 Pneumocystis jiroveci pneumonia.

2 Decreasing (secondary to improved prophylaxis and widespread use of highly active antiviral therapy)

3 CD4 less than 200/mm³.

Reference

Aviram G, Fishman JE, Boiselle PM: Thoracic infections in human immunodeficiency virus/acquired immune deficiency syndrome. Semin Roentgenol 42:23-36, 2007.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, p 128.

Comment

The classic chest radiographic presentation of Pneumocystis pneumonia is a bilateral perihilar or diffuse symmetric interstitial pattern, which may be finely granular, reticular, or ground glass in appearance. Importantly, the chest radiograph may be normal at the time of presentation in a significant minority of cases of Pneumocystis pneumonia. CT, particularly HRCT, is more sensitive than chest radiographs for detecting Pneumocystis pneumonia and thus may be helpful in evaluating symptomatic patients with normal or equivocal radiographic findings.

The classic CT finding in Pneumocystis pneumonia is extensive ground-glass attenuation, which corresponds to the presence of intraalveolar exudate, consisting of fluid, organisms, and debris. It is often distributed in a patchy or geographic fashion, with a predilection for the central, perihilar regions of the lungs. Ground-glass attenuation is occasionally accompanied by thickened septal lines, and foci of consolidation may also be evident in severe cases. In up to a third of cases of Pneumocystis pneumonia, ground-glass opacities are accompanied by cystic lung disease. Such cysts have an upper lobe predominance and demonstrate varying sizes and wall thicknesses.

Case 59

1 Name four benign causes of calcified lymph nodes.

2 In patients with lymphoma, are calcified lymph nodes usually seen before or after radiation therapy?

3 Name a neoplasm that can result in ossified lymph nodes.

4 Which lymph node group is involved in the second figure?

Answers

Case 59

Ossified Lymph Nodes Secondary to Metastatic Osteosarcoma

1 TB, histoplasmosis, sarcoidosis, and silicosis.

3 Osteosarcoma.

4 Superior diaphragmatic nodes.

Reference

Johnson GL, Askin FB, Fishman EK: Thoracic involvement from osteosarcoma: typical and atypical CT manifestations. AJR Am J Roentgenol 168:347-349, 1997.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, p 353.

Comment

Calcified lymph nodes are usually benign, and they are often related to granulomatous processes, such as TB, histoplasmosis, or sarcoidosis. Neoplastic causes of calcified lymph nodes are less common. They include metastases from mucinous adenocarcinomas and lymphoma. With regard to lymphoma, calcification is frequently seen following radiation therapy, but it is rarely encountered in untreated cases.

Ossified lymph nodes are a rare manifestation of metastatic osteosarcoma. Such nodes appear similar to calcified lymph nodes. In patients with osteosarcoma, the presence of lymph node metastases portends a poor prognosis. Lymphatic involvement is usually accompanied by metastases within the lung, a common site of metastases. Lung metastases frequently demonstrate ossification.

Case 60

1 Name two types of infections that may result in rapidly growing nodules in a non-AIDS immunosuppressed patient.

2 What organism is most closely associated with septic infarcts?

3 Name two common sources of septic infarcts.

4 List four CT features of septic infarcts.

Answers

Case 60

Septic Infarcts

1 Fungal (Aspergillus, Mucor); septic infarcts.

2 Staphylococcus aureus.

3 Tricuspid endocarditis (often seen in intravenous drug abusers) and indwelling catheters and prosthetic devices.

4 Poorly defined nodules that frequently cavitate, wedge-shaped foci of consolidation, peripheral and basilar predominance, and feeding vessel.

Reference

Engelke C, Schaefer-Prokop C, Schirg E, et al: High-resolution CT and CT angiography of peripheral pulmonary vascular disorders. Radiographics 22:739-764, 2002.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, pp 84, 85.

Comment

Septic infarcts most often originate from right-sided tricuspid endocarditis or from infected thrombi within systemic veins. Other sources include septal defects, central venous catheters, and pacemaker wires. On chest radiographs and CT scans of patients with septic infarcts, you may observe poorly defined nodular opacities and areas of wedge-shaped parenchymal opacification. Such opacities are usually peripheral in location, and they have a predilection for the lower lobes. Cavitation is frequently observed, particularly on CT scans. A characteristic finding on CT scans is the identification of feeding vessels leading to the nodules (arrows in the second figure) and wedge-shaped parenchymal opacities. Thus, the CT finding of cavitating nodules with feeding vessels is highly suggestive of septic infarcts.

Case 61

1 What postoperative complication is evident in this case (the first radiograph was obtained prior to the second)?

2 Is bronchopleural fistula more common following left- or right-sided pneumonectomy?

3 List four radiographic signs of bronchopleural fistula following pneumonectomy.

4 What nuclear medicine study can be helpful in confirming this diagnosis?

Answers

Case 61

Bronchopleural Fistula

1 Bronchopleural fistula.

3 Failure of the pneumonectomy space to fill with fluid; abrupt decrease in the air-fluid level in the pneumonectomy space; contralateral shift of the mediastinum following pneumonectomy; and identification of air in a previously completely opacified pneumonectomy space.

4 Xenon ventilation study.

Reference

Chae EJ, Seo JB, Kim SY, et al: Radiographic and CT findings of thoracic complications after pneumonectomy. Radiographics 26:1449-1468, 2006.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, pp 166-167.

Comment

Bronchopleural fistula is a relatively uncommon but serious complication following pneumonectomy, with a prevalence of up to 5% and a mortality rate of approximately 20%. Major predisposing factors relate to operative causes of bronchial ischemia, such as a long bronchial stump, too proximal a ligation of the bronchial arteries, and disruption of bronchial blood supply from extensive lymph node dissection. Additional risk factors include preoperative radiation therapy, steroid therapy, malnutrition, and resection through tumor or infection.

Following pneumonectomy, the mediastinum is normally shifted toward the side of resection, and the pneumonectomy space gradually fills with fluid over time. Bronchopleural fistula should be considered when any of the following are observed: (1) the pneumonectomy space fails to fill with fluid; (2) there is an abrupt decrease in the air-fluid level in the pneumonectomy space; (3) there is a new collection of air in a previously opacified pneumonectomy space; or (4) there is contralateral shift of the mediastinum. The diagnosis can be confirmed with a xenon ventilation study, which will demonstrate xenon activity in the pneumonectomy space.

Case 62

1 What is the most common cell type of bronchogenic carcinoma to present in this location?

2 Does the presence of chest wall invasion make this an inoperable lesion?

3 Name at least two absolute contraindications to surgical resection of superior sulcus tumors.

4 What imaging modality is best suited for determining the resectability of a superior sulcus tumor?

Answers

Case 62

Superior Sulcus Tumor

1 Squamous cell carcinoma.

3 Invasion of more than 50% of a vertebral body, brachial plexus invasion above T1 nerve level, esophageal invasion, tracheal invasion.

References

Bruzzi JF, Komaki R, Walsh GL, et al: Imaging of non–small cell lung cancer of the superior sulcus. Part 1: anatomy, clinical manifestations and management. Radiographics 28:551-560, 2008.

Bruzzi JF, Komaki R, Walsh GL, et al: Imaging of non–small cell lung cancer of the superior sulcus. Part 2: initial staging and assessment of respectability and therapeutic response. Radiographics 28:561-572, 2008.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, p 265.

Comment

A lung cancer arising at the extreme apex of the lung is referred to as a superior sulcus tumor. Affected patients typically present with symptoms of shoulder pain, Horner’s syndrome (ptosis, miosis, anhidrosis), and weakness and atrophy of intrinsic muscles of the hand.

MRI is more accurate than CT for determining the resectability of a superior sulcus tumor owing to its superior ability to evaluate tumor extension in the neural foramina, spinal cord, and brachial plexus. PET-CT allows for detection of nodal and distant metastases and is thus helpful for staging.

In this case, note the presence of rib destruction adjacent to the mass (best visualized on the coned-down image), indicative of chest wall invasion. Chest wall invasion is an important preoperative finding, but it does not preclude surgical resection of a superior sulcus tumor.

Operable candidates are usually treated with preoperative radiation and chemotherapy followed by surgery with chest wall resection.

Case 63

1 What is the most likely cause for these HRCT findings?

2 Approximately what percentage of patients with this disorder are cigarette smokers?

3 In patients with this disorder, which portion of the lungs is usually spared?

4 Would you expect this patient to have diminished lung volumes?

Answers

Case 63

Pulmonary Langerhans Cell Histiocytosis (LCH)

1 Pulmonary LCH.

2 Approximately 90%.

3 Lung bases and costophrenic angles.

Reference

Abbott GF, Rosado-de-Christenson ML, Franks TJ, et al: From the archives of the AFIP: pulmonary Langerhans cell histiocytosis. Radiographics 24:821-841, 2004.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, pp 196-198.

Comment

Pulmonary Langerhans cell histiocytosis (PLCH) is an uncommon idiopathic disorder characterized histologically by the benign proliferation of mature histiocytes. In its early stages, PLCH is characterized by the presence of multiple granulomatous nodules, which are often peribronchiolar in distribution. In later stages of the disease, the nodules are replaced by cysts.

Affected patients are usually young and middle-aged adults, and there is a strong association with cigarette smoking. Symptoms include dyspnea and dry cough.

On conventional radiographs, PLCH manifests as a reticulonodular pattern, with the upper lobes affected to a greater degree than the lower lobes. The lung bases and costophrenic angles are typically spared. Lung volumes are usually normal or increased.

HRCT demonstrates small irregular nodules that are typically centrilobular and peribronchiolar in distribution. Such nodules may undergo cavitation, and may eventually form thin-walled cysts. Cysts associated with PLCH are less uniform in appearance than cysts associated with LAM. Because nodules are not a feature of LAM, the identification of both nodules and cysts should suggest the diagnosis of PLCH.

Case 64

1 Name three possible diagnoses for the chest radiograph findings in this patient with breast cancer who is receiving chemotherapy.

2 Based on the HRCT findings, which diagnosis is most likely?

3 Name four sites of primary malignant neoplasms that are commonly associated with lymphangitic carcinomatosis.

4 Which primary neoplasm is most closely associated with a unilateral distribution of lymphangitic carcinomatosis?

Answers

Case 64

Lymphangitic Carcinomatosis

1 Lymphangitic carcinomatosis, atypical infection, and drug toxicity.

2 Lymphangitic carcinomatosis.

3 Colon, lung, breast, and stomach.

Reference

Müller NL, Silva CIS: Pulmonary metastases. In: Silva CIS, Müller NL, Eds. Imaging of the Chest. Philadelphia, Saunders, 2008, pp 568-581.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, pp 190-192.

Comment

Pulmonary lymphangitic carcinomatosis refers to tumor growth within the lymphatics of the lungs. Interestingly, most lymphangitic metastases are thought to arise from hematogenous spread. Lymphangitic carcinomatosis occurs most commonly in patients with carcinoma of the colon, lung, breast, and stomach and adenocarcinoma of unknown primary.

The chest radiographic findings of lymphangitic carcinomatosis are nonspecific. They include diffuse reticulonodular or linear opacities, septal lines, hilar and mediastinal lymph node enlargement, and pleural effusions.

The HRCT findings of lymphangitic carcinomatosis are more specific. The observed abnormalities reflect the distribution of lymphatics within the lung: (1) smooth or nodular axial interstitial thickening along the bronchovascular bundles; (2) smooth or nodular interlobular septal thickening; (3) smooth or nodular thickening of the fissures; and (4) identification of polygonal structures (secondary pulmonary lobules). An important ancillary observation is the preservation of normal lung architecture.

Case 65

1 What is the most likely diagnosis for these imaging findings?

2 What are “satellite” nodules?

3 What is their significance?

4 What are the most common sites for post-primary TB in the lung?

Answers

Case 65

Reactivation TB

2 Small, often rounded, opacities that lie in close proximity to a larger nodule or mass.

3 They are more suggestive of an infectious process, such as TB, than a lung carcinoma.

4 Apical and posterior segments of the upper lobes and superior segments of the lower lobes.

Reference

Lee JY, Lee KS, Jung KJ, et al: Pulmonary tuberculosis: CT and pathologic correlation. J Comput Assist Tomogr 24:691-698, 2000.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, pp 102-104.

Comment

The chest radiograph demonstrates a poorly marginated mass in the right lung apex, without evidence of calcification. CT is often helpful to further characterize a lung nodule or mass. In this case, CT reveals a focus of cavitation that is not apparent on the conventional radiograph. There are also two important ancillary findings on the CT image. First, there are several small nodules adjacent to the mass. Such nodules are referred to as satellite nodules, and their presence suggests an infectious etiology, such as TB, rather than a lung carcinoma. However, the term satellite nodules may also be used to describe foci of malignancy within the primary tumor lobe. Thus, satellite nodules are not pathognomonic for infection. Second, note the presence of numerous small, centrilobular, linear and branching, Y- and V-shaped opacities, a pattern that is also referred to as tree-in-bud. This pattern is often associated with bronchogenic spread of TB, a type of dissemination that occurs when a cavity erodes into an adjacent airway. Thus, the combination of an apical lung cavity, satellite nodules, and a tree-in-bud pattern is highly suggestive of post-primary TB.

Case 66

1 What is the most likely cause of the precarinal and right hilar masses?

2 Do MRI signal characteristics of lymph nodes effectively distinguish between benign and malignant lymph nodes?

3 Is MRI more accurate than CT in the assessment of mediastinal lymph nodes in patients with lung cancer?

4 Which imaging test is more accurate than MRI and CT in the assessment at mediastinal lymph nodes in patients with lung cancer?

Answers

Case 66

Mediastinal and Hilar Lymph Node Enlargement in a Patient With Primary Lung Cancer

1 Mediastinal and hilar lymph node enlargement.

4 FDG–PET imaging.

Reference

Lardinois D, Weder W, Hany TF, et al: Staging of non–small-cell lung cancer with integrated positron-emission tomography and computed tomography. N Engl J Med 348:2500-2507, 2003.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, pp 266-268, 352-353.

Comment

Lymph node enlargement is a common cause of a mediastinal or hilar mass and should be suspected whenever a spherical or ovoid mass or masses are identified within a known anatomic lymph node location. There are a variety of infectious, inflammatory, and neoplastic causes of thoracic lymph node enlargement.

Neoplastic etiologies include primary lung cancer, metastatic disease, and lymphoma. This patient has a primary lung cancer in the right upper lobe (not shown on these images), and the lymph nodes were proved malignant at biopsy.

Both CT and MRI rely on anatomic features of lymph nodes, most notably lymph node size (short axis larger than 1 cm), to distinguish between malignant and benign lymph nodes. This strategy is limited by a low sensitivity and specificity. Thus, in patients with primary lung cancer, enlarged nodes must be biopsied for staging purposes. FDG-PET imaging, which relies upon metabolic (glucose metabolism) rather than anatomic features, is the most accurate noninvasive imaging test for assessing mediastinal lymph nodes. The accuracy of FDG-PET can be further enhanced by using an integrated PET-CT scanner, which improves visual quality and quantitative accuracy of PET images, while optimizing anatomic-metabolic correlation.

Case 67

1 What is the cause of diffuse mediastinal widening in this patient?

2 Does this disorder require therapy?

3 Name three risk factors for developing this condition.

4 Where does excess fat usually accumulate in patients with this condition?

Answers

Case 67

Mediastinal Lipomatosis

1 Mediastinal lipomatosis.

3 Cushing’s syndrome, steroid therapy, and obesity.

4 Anterior and superior mediastinum, cardiophrenic angles, and paravertebral and retrocrural regions.

Reference

Boiselle PM, Rosado-de-Christenson ML: Fat attenuation lesions of the mediastinum. J Comput Assist Tomogr 25:881-889, 2001.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, pp 369-370.

Comment

The chest radiograph demonstrates a right upper lobe pneumonia and diffuse mediastinal widening. There are a variety of causes of mediastinal widening, including mediastinal lipomatosis, mediastinitis, diffuse mediastinal lymphadenopathy, and mediastinal hemorrhage. The widened mediastinum is relatively symmetric in appearance, and there is no deviation of the trachea. Such features are typical of mediastinal lipomatosis, but a definitive diagnosis requires demonstration of fat by CT or MRI. The CT image confirms the diagnosis of mediastinal lipomatosis.

Mediastinal lipomatosis refers to the diffuse accumulation of excess unencapsulated fat within the mediastinum. Fat accumulation is usually most prominent in the anterior and superior portions of the mediastinum. Fat may also accumulate in other parts of the mediastinum, including the cardiophrenic angles and the paravertebral region. An important diagnostic feature is the homogeneous appearance of the mediastinal fat. A heterogeneous appearance should raise the suspicion of another superimposed process, such as mediastinal hemorrhage or neoplastic infiltration of the mediastinal fat.

Case 68

1 What congenital vascular abnormality is evident in this case?

2 Which mediastinal interface is typically displaced in patients with this condition?

3 Name an associated extravascular abnormality that is present on the CT image of the abdomen.

4 Name at least two additional causes of azygos vein enlargement.

Answers

Case 68

Azygos Continuation of the Inferior Vena Cava

1 Azygos continuation of the inferior vena cava.

2 Azygoesophageal interface.

4 Obstruction of the vena cava, tricuspid insufficiency, and right-sided heart failure.

Reference

Kandpal H, Sharma R, Gamangatti S, et al: Imaging the inferior vena cava: a road less traveled. Radiographics 28:669-689, 2008.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, pp 364, 365.

Comment

The chest radiograph and thoracic CT image demonstrate marked distention of the arch of the azygos vein. The abdominal CT image shows dilation of the retrocrural portion of the azygos vein (arrow) and absence of a definable inferior vena cava. The constellation of findings is diagnostic of azygos continuation of the inferior vena cava, a congenital anomaly that is associated with both the asplenia and the polysplenia syndromes. Note multiple spleens in the left upper quadrant of the abdomen on the abdominal CT image.

On chest radiographs of affected patients, you will observe widening of the azygos arch contour and displacement of the azygoesophageal recess below this level. CT can confirm the diagnosis by demonstrating absence of a definable inferior vena cava. CT is also helpful in excluding other causes of azygos vein distention such as obstruction of the vena cava.

Knowledge of this congenital anomaly is important preoperatively for planning cardiopulmonary bypass surgery and may also help to avoid difficulties at cardiac catheterization.

Case 69

1 How would you describe the margins of this nodule?

2 Precontrast and 1-minute postcontrast images demonstrate nodule enhancement of 35 Hounsfield units. Is this degree of enhancement diagnostic of a benign entity?

3 Which noninvasive test has a higher specificity for malignancy: FDG-PET or CT pulmonary nodule enhancement?

4 Does CT pulmonary nodule enhancement have a high or low negative predictive value for malignancy?

Answers

Case 69

CT Pulmonary Nodule Enhancement

4 High negative predictive value.

Reference

Swensen SJ, Viggiano RW, Midthun DE, et al: Lung nodule enhancement at CT: multicenter study. Radiology 214:73-80, 2000.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, pp 284-286.

Comment

The CT images demonstrate a lung nodule with lobulated margins, which enhances by 35 Hounsfield units. The degree of enhancement is greater than the 15 Hounsfield unit threshold for this test and is thus of concern for a malignant process.

CT pulmonary nodule enhancement is a relatively new, noninvasive technique that relies on the principle that malignant nodules are generally more vascular than benign nodules, such as granulomas. This technique requires meticulous attention to the study protocol described by Swensen and colleagues. The protocol employs the use of serial spiral CT acquisitions (3 mm collimation) before and at four sequential 1-minute intervals following the intravenous administration of contrast. Nodule enhancement values are obtained by placing a region of interest measurement within the nodule center. Enhancement less than 15 Hounsfield units is highly predictive of a benign process (negative predictive value for malignancy is 96%). Enhancement greater than 15 Hounsfield units is of concern for malignancy, but the specificity is only moderate (58%). Such enhancing nodules generally require further assessment, such as biopsy or surgical resection.

Because of the need for multiple imaging acquisitions and close monitoring of the scanning and measurement protocols, this technique has not gained widespread use in clinical practice. However, recent technical advances in dual-energy CT, which allow measurement of the degree of nodule enhancement from a single CT acquisition, have the potential to expand the clinical use of CT nodule enhancement in differentiating between benign and malignant lung nodules.

Case 70

1 Which hemidiaphragm is more often affected by traumatic rupture, the left or the right?

2 What are the two most common causes of diaphragm rupture?

3 In patients with traumatic rupture of the left hemidiaphragm, which organ is most commonly herniated?

4 Name five radiographic signs of left hemidiaphragm rupture.

Answers

Case 70

Traumatic Rupture of the Left Hemidiaphragm

2 Blunt trauma and penetrating injury.

4 Nasogastric tube coiled in the thorax, apparent elevation of the hemidiaphragm with loss of its normal dome shape, changing hemidiaphragm levels on serial radiographs, contralateral mediastinal shift, and left pleural effusion.

Reference

Kaewlai R, Avery LL, Asrani AV, Novelline RA: Multidetector CT of blunt thoracic trauma. Radiographics 28:1555-1570, 2008.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, pp 169-170, 173-175.

Comment

Diaphragmatic rupture is an uncommon but serious complication of blunt and penetrating trauma. The left hemidiaphragm is affected more often than the right side. The left-sided predominance is thought to be secondary to two factors: a protective effect from the liver on the right side and relative weakness of the left hemidiaphragm compared with the right.

Because of the morbidity and mortality from associated bowel obstruction and strangulation, a prompt diagnosis of diaphragm rupture is important. Unfortunately, however, the diagnosis is often delayed. You should suspect this diagnosis when you observe apparent elevation of a hemidiaphragm, changing hemidiaphragm levels on serial radiographs, or an unusual contour of the hemidiaphragm. A more specific finding is the identification of stomach or bowel in the thorax. CT or MRI can confirm the diagnosis. Although the direct multiplanar imaging capability of MRI was previously a major advantage compared with CT, the high-quality multiplanar reformations that can now be obtained with thin-section MDCT scanners allow for improved sensitivity and specificity of diagnosing diaphragmatic injury using CT. Because MDCT is better suited to evaluating clinically unstable patients than MRI, CT is currently the preferred imaging test for suspected diaphragm injury in the acute trauma setting.

Case 71

1 What skeletal injury is evident on these CT images?

2 Which is more common—anterior or posterior dislocation?

3 Name a potential complication of posterior dislocation.

4 What is the best imaging test for establishing or confirming a diagnosis of sternoclavicular joint dislocation?

Answers

Case 71

Posterior Sternoclavicular Joint Dislocation

1 Left posterior sternoclavicular joint dislocation.

3 Injury to the brachiocephalic or subclavian veins. Less commonly, injury to the trachea or esophagus.

Reference

Kaewlai R, Avery LL, Asrani AV, Novelline RA: Multidetector CT of blunt thoracic trauma. Radiographics 28:1555-1570, 2008.

Cross-Reference

Comment

Sternoclavicular joint dislocation is a relatively uncommon but potentially serious injury that is usually associated with massive direct trauma to the anterior chest wall. Affected patients typically present with a large hematoma of the upper anterior chest wall and asymmetry of the clavicles on palpation (especially in the setting of an anterior dislocation).

The diagnosis can be difficult to make on portable chest radiographs, because only minimal displacement is usually evident on such studies. Moreover, the sternoclavicular joints are often altered in appearance radiographically on the basis of patient rotation. When this injury is suspected on the basis of clinical or radiographic findings, a limited CT study through the level of the sternoclavicular joints can readily establish the diagnosis. In the setting of a posterior dislocation, contrast-enhanced CT also provides an assessment of the brachiocephalic and subclavian veins for signs of injury.

Case 72

1 Is pulmonary embolus the most common cause of unilateral absent perfusion on a ventilation-perfusion (

2 What is the cause in this case?

3 What entities are associated with ascending aortic aneurysms?

4 What other aortic abnormality can result in this scintigraphic appearance?

Answers

Case 72

Right Pulmonary Artery Compression by Ascending Aortic Aneurysm

2 Ascending aortic aneurysm.

3 Connective tissue disorders (Marfan’s and Ehlers-Danlos syndromes) and syphilis.

4 Aortic dissection.

Reference

Pickhardt PJ, Fischer KC: Unilateral hypoperfusion or absent perfusion on pulmonary scintigraphy: differential diagnosis. AJR Am J Roentgenol 171:145-150, 1998.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, pp 358-359.

Comment

A variety of entities may result in the presence of unilateral absence of perfusion on pulmonary scintigraphy scans. Interestingly, thromboembolism accounts for only a minority of such cases. Nonthromboembolic causes include mediastinal and hilar masses, ascending aortic aneurysm and dissection, pulmonary artery hypoplasia and agenesis, pulmonary artery sarcoma, and pneumonectomy. When confronted with this pattern on a pulmonary scintigraphy study, you should carefully assess the chest radiograph for the presence of a nonthromboembolic cause, such as a central mass. CT is often helpful for further evaluation, because it can readily distinguish between an intrinsic filling defect of the pulmonary artery and an extrinsic compression of the vessel.

In this case, absent perfusion to the right lung is caused by severe compression of the right pulmonary artery by an ascending aortic aneurysm. Ascending aortic aneurysms are usually associated with connective tissue disorders such as Marfan’s and Ehlers-Danlos syndromes. Syphilis is an infrequent cause of ascending aortic aneurysm. Right pulmonary artery compression is an uncommon complication of ascending aortic aneurysm. More common complications include rupture, dissection, aortic insufficiency, and pericardial tamponade.

Case 73

1 What does the circular lucency (arrows) adjacent to the tracheostomy tube represent?

2 Name at least two potential complications of an overinflated tracheostomy tube or endotracheal tube cuff.

3 Name two types of fistulas that may occur as a tracheostomy tube complication.

4 What is the ideal location for the tip of a tracheostomy tube?

Answers

Case 73

Overinflated Tracheostomy Tube Cuff

1 An overinflated tracheostomy tube cuff.

2 Tracheal stricture, tracheomalacia, tracheal rupture, and tracheoesophageal fistula.

3 Tracheoesophageal and tracheoarterial.

4 The tip should ideally be positioned halfway between the stoma and the carina.

Reference

Sun M, Ernst A, Boiselle PM: MDCT of the central airways: comparison with bronchoscopy in the evaluation of complications of endotracheal and tracheostomy tubes. J Thorac Imaging 22:136-142, 2007.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, pp 292-294.

Comment

A tracheostomy tube is usually placed for long-term ventilatory support or to establish an airway distal to the presence of a laryngeal obstruction. Most long-term complications of intubation relate to cuff injury. In recent years, the advent of low-pressure, high-volume cuffs has been associated with a decreased rate of cuff complications.

If the cuff is overinflated, blood supply to the mucosa of the trachea is compromised, leading to ischemic necrosis. Late complications of ischemic necrosis include tracheal stricture and tracheomalacia.

A second mechanism of airway injury relates to abnormal angulation of the tube. This problem occurs more frequently with tracheostomy tubes than with endotracheal tubes. Angulation of the tube can result in erosion, ulceration, and eventual perforation of the tracheal wall. Posterior angulation can lead to a tracheoesophageal fistula, and anterolateral angulation can result in a tracheoarterial fistula with either the innominate or the carotid artery. Rarely, an overinflated cuff can directly erode a vessel and result in a tracheoarterial fistula. In this particular case, an overinflated cuff resulted in a tracheocarotid fistula, which proved fatal.

MDCT is highly accurate for detecting complications of endotracheal and tracheostomy tubes, especially when axial CT images are combined with multiplanar and three-dimensional reconstructions.

Case 74

1 What is the most likely cause for the parenchymal abnormality observed in the right lower lobe in this patient?

2 Name the term that is used to describe the whorled appearance of the adjacent bronchovascular bundles.

3 What occupational exposure is most closely related to this process?

4 Is rounded atelectasis associated only with asbestos-related pleural disease?

Answers

Case 74

Rounded Atelectasis

1 Rounded atelectasis.

2 The “comet tail sign.”

Reference

Batra P, Brown K, Hayashi K, Mori M: Rounded atelectasis. J Thorac Imaging 11:187-197, 1996.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, pp 211-212.

Comment

Rounded atelectasis refers to a form of peripheral focal atelectasis that develops in patients with pleural disease. Although it is most commonly associated with asbestos-related pleural disease, rounded atelectasis may occur in the setting of chronic pleural thickening or effusion from any etiology.

On chest radiography, it typically appears as a subpleural round or oval, sharply marginated mass that occurs most commonly in the posterior aspect of the lower lobes. The mass usually abuts an area of pleural thickening, which is usually greatest in dimension near the mass. The mass forms acute angles with the adjacent lung parenchyma and is usually separated from the diaphragm by interposed aerated lung.

A characteristic feature of rounded atelectasis is the presence of a curvilinear tail, which has been referred to as the comet tail sign. This refers to the presence of crowded bronchi and blood vessels that extend from the lower border of the mass and converge to the adjacent hilum, creating a whorled appearance of the bronchovascular bundle. Signs of volume loss are occasionally evident on chest radiography but are usually minimal. On CT, displacement of the adjacent fissure is frequently observed.

In this case, the CT findings of a focal parenchymal opacity adjacent to an area of pleural thickening with associated volume loss and a comet tail sign are diagnostic of rounded atelectasis. For cases in which the CT findings are equivocal, fine-needle aspiration biopsy is suggested to exclude malignancy because of the high association between lung cancer and asbestos exposure in smokers. PET imaging typically shows no FDG avidity, but low-level uptake has been described in some cases.

Case 75

1 Name at least four causes of an upper zone distribution of chronic infiltrative lung disease.

2 Which of these entities are most closely associated with a reticular and nodular pattern on chest radiographs?

3 What is the term used to describe irregular bronchial dilation associated with pulmonary fibrosis?

4 What laboratory test is usually elevated in patients with sarcoidosis?

Answers

Case 75

Sarcoidosis

1 Silicosis, coal worker’s pneumoconiosis, sarcoidosis, ankylosing spondylitis, Langerhans cell histiocytosis (LCH), and chronic berylliosis.

2 Sarcoidosis and LCH.

3 Traction bronchiectasis.

4 Angiotensin-converting enzyme (ACE) levels.

Reference

Miller BH, Rosado-de-Christenson ML, McAdams HP, Fishback NF: Thoracic sarcoidosis: radiologic-pathologic correlation. Radiographics 15:421-437, 1995.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, pp 188-190.

Comment

The chest radiograph reveals a bilateral upper lung zone distribution of reticular and nodular opacities with associated upper lobe volume loss. The HRCT images in the second and third figures demonstrate irregular linear and small nodular opacities with associated architectural distortion and traction bronchiectasis and bronchiolectasis.

Among the various causes of an upper lung zone distribution of chronic infiltrative lung disease, sarcoidosis is most closely associated with a reticular and nodular pattern. Approximately 20% of sarcoid patients with evidence of interstitial lung disease will develop fibrosis. The fibrosis is usually most pronounced in the apical and posterior portions of the upper lobes and in the superior segments of the lower lobes, as demonstrated in this case. Signs of volume loss and architectural distortion are commonly observed, with masslike opacities and areas of traction bronchiectasis.

Case 76

1 What vascular abnormality is evident on this MRI?

2 Name at least two entities that may be associated with an ascending aortic aneurysm.

3 Is this a T1W or a T2W image?

4 What is the difference between a true and a false aneurysm?

Answers

Case 76

Ascending Aortic Aneurysm Secondary to Cystic Medial Necrosis

1 Ascending aortic aneurysm.

2 Cystic medial necrosis (Marfan’s and Ehlers-Danlos syndromes), atherosclerosis, and syphilis.

3 T1W (note the bright signal intensity of mediastinal fat).

4 A true aneurysm has an intact aortic wall; a false aneurysm is characterized by a disrupted aortic wall.

Reference

Agarwal PP, Chughtal A, Matzinger F, Karerooni EA: Multidetector CT of thoracic aortic aneurysms. Radiographics 29:537-552, 2009.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, pp 358-359.

Comment

The coronal MRI in the figure reveals marked aneurysmal dilation of the ascending aorta. An aneurysm is defined as an abnormal dilation of a vessel. With regard to the ascending aorta, there is some variability in diameter with increasing patient age, but a diameter of greater than 4 cm is generally considered abnormal.

Aneurysms may be classified on the basis of the integrity of aorta wall (true vs. false), location, and shape. With regard to shape, fusiform aneurysms are characterized by cylindrical dilation of the entire circumference of the aorta, and saccular aneurysms are characterized by a focal outpouching of the aorta. Fusiform aneurysms are most commonly associated with atherosclerosis, whereas saccular aneurysms are most often traumatic or infections in etiology.

Ascending aortic aneurysms are less common than descending thoracic aortic aneurysms. Although aneurysmal dilation of the ascending aorta is frequently caused by atherosclerosis, this process usually involves other portions of the aorta as well. Annuloaortic ectasia refers to the presence of dilated sinuses of Valsalva with effacement of the sinotubular junction, resulting in a pear-shaped ascending aorta that tapers to a normal-caliber aortic arch. This disorder may be idiopathic or associated with connective tissue disorders such as Ehlers-Danlos and Marfan’s syndromes. Syphilis, once a relatively common cause of ascending aortic aneurysms, is now rare.

The major complication of aneurysms is rupture. The risk of rupture is related to the size of the aneurysm. For this reason, elective surgical repair is generally recommended when aneurysms exceed 5 to 6 cm in diameter.

Case 77

1 Which pulmonary neoplasm is the most likely cause for this centrally obstructing mass that contains calcification?

2 Are carcinoids benign or malignant neoplasms?

3 Name the nuclear medicine study that can be useful for imaging carcinoid tumors.

4 What percentage of carcinoids demonstrate calcification on CT images?

Answers

Case 77

Carcinoid

3 Octreotide scanning.

4 Approximately 30%.

Reference

Chong S, Lee KS, Chung MJ, et al: Neuroendocrine tumors of the lung: clinical, pathologic, and imaging findings. Radiographics 26:41-57, 2006.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, pp 269-270.

Comment

The frontal chest radiograph demonstrates a central, right hilar mass with associated partial atelectasis of the right upper lobe. The CT image demonstrates a partially calcified right hilar mass that obstructs the right upper lobe bronchus. The imaging features are characteristic of a central carcinoid tumor.

Bronchial carcinoid tumors are uncommon neuroendocrine neoplasms that occur centrally (80%) more commonly than peripherally (20%). Affected patients are usually in the third to seventh decade of life and typically present with cough, hemoptysis, and postobstructive pneumonia.

On chest radiographs, carcinoids typically appear as a central, hilar, or perihilar mass that may be associated with postobstructive atelectasis, pneumonia, mucoid impaction, or bronchiectasis. On CT, carcinoids typically demonstrate well-defined margins and slightly lobulated borders. Carcinoids are usually located close to the central bronchi, usually near airway bifurcations. Calcification is observed in approximately 30% of cases on CT but is not usually evident on conventional radiographs. Most lesions demonstrate intense contrast enhancement.

A minority of carcinoids present as a solitary pulmonary nodule (SPN) in the periphery of the lung. Typical carcinoid tumors in the periphery of the lungs usually grow at a slow rate. Atypical carcinoids, which account for 10% of all carcinoids, occur most often in the lung periphery. These lesions are usually large at the time of presentation and grow at a faster rate than typical carcinoids. Although typical carcinoids rarely metastasize, atypical carcinoids exhibit metastases in up to half of patients.

Therapy of carcinoid tumors consists of surgical resection, with a more aggressive surgical approach for atypical lesions. Adjuvant chemotherapy has also been employed with some success in patients with advanced atypical carcinoid tumors. Typical carcinoids have an excellent prognosis, with a 5-year survival of approximately 90%. In contrast, atypical carcinoids are associated with a 5-year survival of approximately 70%.

Because carcinoid tumors have a high number of somatostatin receptors, scintigraphic imaging with the radiolabeled somatostatin analogue octreotide may be helpful for detecting occult tumors. Conversely, PET-FDG imaging is less useful in this setting because of a high rate of false-negative results for typical carcinoid tumors.

Case 78

1 Name the syndrome that refers to esophageal perforation due to repeated episodes of vomiting.

2 Name at least three other causes of esophageal perforation.

3 Name two sites of abnormal, extraalveolar air collections that may be associated with esophageal perforation.

4 Are pleural complications of esophageal perforation more commonly left- or right-sided?

Answers

Case 78

Boerhaave’s Syndrome

1 Boerhaave’s syndrome.

2 Iatrogenic, impacted foreign body, obstructing neoplasm, and trauma.

3 Pneumomediastinum and pneumothorax.

Reference

Giménez A, Franquet T, Erasmus JJ, et al: Thoracic complications of esophageal disorders. Radiographics 22:S247-S258, 2002.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, pp 370, 371.

Comment

Esophageal perforation is a common cause of acute mediastinitis and may occur secondary to a variety of mechanisms. Boerhaave’s syndrome refers to transmural perforation of the distal esophagus that occurs secondary to repeated episodes of vomiting. Rupture typically occurs posteriorly, near the left diaphragmatic crus.

Patients with esophageal perforation typically present with symptoms of fever, leukocytosis, dysphagia, and retrosternal chest pain, which often radiates into the neck. Pneumomediastinum is a frequent chest radiographic finding, as demonstrated in this case (note the presence of an abnormal lucency surrounding the ascending aorta and aortic arch and extending into the soft tissues of the lower neck). Additional chest radiographic findings may include diffuse mediastinal widening, pneumothorax (note the presence of a left hydropneumothorax in the figure), pleural effusion, and empyema. When the diagnosis of esophageal perforation is delayed, additional complications may include mediastinal abscess, esophagopleural fistula, and esophagobronchial fistula.

A diagnosis of suspected esophageal perforation can be confirmed by performing a fluoroscopic examination of the esophagus following the administration of water-soluble contrast medium. Such a study demonstrates extravasation of contrast at the site of perforation, but it may be false-negative in up to 10% of cases. CT may be helpful in cases for which fluoroscopy is nondiagnostic. It may also be helpful to delineate the location and extent of fluid collections in cases that have progressed to mediastinal abscess formation.

It is important to be aware that a delay of more than 24 hours in the diagnosis of this complication is associated with high morbidity and mortality rates. Thus, prompt diagnosis and treatment are critical.

Case 79

1 In an HIV-positive patient, what is the most likely cause for these CT findings?

2 What organ system is most commonly involved by this neoplasm?

3 Name the demographic group of HIV-positive patients that is most commonly affected by this neoplasm.

4 Is Kaposi’s sarcoma (KS) gallium-avid?

Answers

Case 79

Kaposi’s Sarcoma

3 Homosexual men.

Reference

Boiselle PM, Aviram G, Fishman JE: Update on lung disease in AIDS. Semin Roentgenol 37:54-71, 2002.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, pp 131, 133.

Comment

KS is the most common AIDS-related neoplasm worldwide, but its prevalence has markedly declined in the Western world owing to widespread use of highly active antiretroviral therapy (HAART). It occurs predominantly, but not exclusively, in homosexual men. KS is a multicentric neoplasm that arises from endothelial cells. It may involve multiple organ systems, including the skin, lymphatics, lungs, and gastrointestinal system. It is associated with human herpesvirus 8, also referred to as Kaposi’s sarcoma herpesvirus.

The CT image in this case demonstrates characteristic lung parenchymal abnormalities of KS, including a peribronchovascular distribution of consolidation and poorly defined lung nodules. Less commonly observed lung parenchymal findings may include interlobular septal thickening and ground-glass attenuation. The latter is usually observed around the perimeter of lung nodules and masses. Pleural effusions and thoracic lymph node enlargement are relatively common thoracic manifestations of KS and frequently accompany pulmonary parenchymal abnormalities.

Nuclear medicine imaging may be helpful in the assessment of HIV-positive patients with suspected pulmonary KS. Unlike pulmonary infections and lymphoma, KS is not gallium-avid. Thus, in an HIV-positive patient with diffuse parenchymal abnormalities, the absence of increased gallium activity within the lungs can help confirm the diagnosis of KS and exclude a coexisting infection or alternative diagnosis such as lymphoma.

Case 80

1 Define a bulla.

2 Define a bleb.

3 Name at least two potential complications of bullae.

4 What is the treatment for symptomatic bullae?

Answers

Case 80

Bulla

1 A bulla is a sharply demarcated airspace measuring more than 1 cm in diameter and possessing a well-defined wall less than 1 mm in thickness.

2 A bleb is a small (less than 1 cm) gas-containing space within the visceral pleura or in the subpleural lung.

3 Pneumothorax, infection, and hemorrhage.

4 Surgical resection (bullectomy).

Reference

Arroliga AC: Lung volume reduction and bullectomy in COPD. In: Rose BD, Ed. UpToDate. Waltham, MA, UpToDate, 2009.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, pp 51, 53, 245, 246.

Comment

The chest radiograph and the CT image demonstrate a large bulla within the right upper lobe.

Bullae may develop in association with any type of emphysema, but they are most commonly associated with paraseptal and centrilobular emphysema. However, they are not always associated with diffuse emphysema.

Bullae usually enlarge over months to years, but the growth rate is quite variable. Occasionally, bullae can become quite large and may be focal in distribution. Large bullae may compromise respiratory function. The resulting syndrome has been referred to by various terms, including bullous emphysema, vanishing lung syndrome, and primary bullous disease of the lung. This entity occurs most often in young men and is characterized by large, progressive upper lobe bullous disease. Although it may occur in nonsmokers, most affected patients are smokers.

CT is the preferred modality for the assessment of patients with suspected bullous emphysema. CT is helpful for delineating the number, size, and location of bullae. It can also assess the degree of compression of underlying normal lung and determine the presence and severity of emphysema in the remaining portion of the lung parenchyma.

In symptomatic patients, surgical resection of bullae can result in marked improvement in pulmonary function. The greatest benefit from surgery is observed in patients with a large bulla (occupying 50% or more of a hemithorax) and a moderate reduction in forced expiratory volume in 1 second (FEV₁). In contrast, patients with severe generalized emphysema tend to do poorly and are thus not ideal candidates for bullectomy.

Case 81

1 What lobe(s) is collapsed in the first figure?

2 What lobe(s) is collapsed in the second figure?

3 In a patient with a known extrathoracic primary neoplasm, what is the likely cause for lobar collapse?

4 Name at least three common sites of primary malignancies that are associated with endobronchial metastases.

Answers

Case 81

Right Middle and Lower Lobe Collapse Secondary to Endobronchial Metastases

1 Right lower lobe.

2 Right middle lobe and right lower lobe.

3 Endobronchial metastases.

4 Kidney, melanoma, thyroid, breast, and colon.

Reference

Seo JB, Im JG, Goo JM, et al: Atypical pulmonary metastases: spectrum of radiologic findings. Radiographics 21:403-417, 2001.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, pp 31-37.

Comment

The chest radiograph in the first figure demonstrates complete collapse of the right lower lobe. A subsequent radiograph (second figure) performed several weeks later reveals combined collapse of the right middle and lower lobes. In the first figure, note the characteristic triangular opacity in the right retrocardiac region that is bordered by a displaced major fissure. The appearance is similar to that observed in cases of left lower lobe collapse. In the second figure, note the further increase in degree of volume loss, with displacement of minor and major fissures, accompanied by increased opacity that obscures the right hemidiaphragmatic contour. The appearance is typical of combined right middle and lower lobe collapse.

Combined right middle and lower lobe collapse can occur when a tumor obstructs the bronchus intermedius. This combination is much more common than combined right upper and right middle lobe collapse because the bronchi to these lobes are remote from one another. When the latter combination occurs, the appearance is identical to left upper lobe collapse.

In this patient, the combined lobar collapse occurred secondary to endobronchial metastatic disease. Also note the presence of pulmonary metastases, best visualized in the left lung. Endobronchial metastases are uncommon and are found in less than 5% of patients at autopsy. Presenting symptoms may include cough, wheeze, and hemoptysis. Coughing may infrequently result in expectoration of tumor fragments; rarely, this is the first indication of metastatic disease.

Radiographic findings in the setting of partial airway obstruction include oligemia and air trapping. In the setting of complete bronchial obstruction, findings include lobar, segmental, or subsegmental atelectasis and postobstructive pneumonitis. A hilar or central mass may also be evident.

Case 82

1 A region-of-interest measurement of this mass demonstrated Hounsfield units consistent with fat attenuation. What are the two most likely diagnoses?

2 How can you explain the spread of this mass into the axilla?

3 Although this mass is predominantly fat attenuation, it contains a few strands of soft tissue attenuation. Does the latter finding exclude the diagnosis of lipoma?

4 What feature of this mass favors a benign diagnosis?

Answers

Case 82

Lipoma

1 Lipoma and liposarcoma.

2 The mass is likely extrapleural in location rather than truly mediastinal and probably spreads over the apex of the lung into the left axilla.

4 Pliability/lack of invasiveness.

Reference

Gaerte SC, Meyer CA, Winer-Muram HT, et al: Fat-containing lesions of the chest. Radiographics 22:S61-S78, 2002.

Cross-Reference

Comment

The CT image demonstrates a fat attenuation mass that contains several strands of soft tissue attenuation. The mass extends into the left axilla, but there is no invasion of the ribs or vessels.

Lipomas may occur in a variety of locations in the thorax, including the mediastinum, chest wall, extrapleural space, esophagus, heart, airway, and rarely, the lung parenchyma. Although lipomas typically appear as well-marginated lesions characterized by homogeneous fat attenuation, soft tissue elements may be observed. In such cases, it may not be possible to distinguish lipoma from thymolipoma or low-grade liposarcoma. The pliability and lack of invasiveness of lipomas may aid in their differentiation from liposarcomas; for example, lipomas typically drape around adjacent vessels, ribs, and mediastinal structures without invading them. In contrast with lipomas, liposarcomas typically contain a larger soft tissue component, have irregular margins, and frequently invade adjacent mediastinal and chest wall structures. Thus, the presence of well-defined margins and lack of invasiveness favor a diagnosis of lipoma over liposarcoma. The diagnosis of lipoma was confirmed at pathology.

Case 83

1 Which type of viral pneumonia typically presents with a diffuse distribution of poorly defined lung nodules?

2 What is the approximate overall incidence of pneumonia in patients with chickenpox?

3 Do pregnant women have a higher or lower incidence of varicella pneumonia than the general population?

4 What is the typical radiographic appearance of healed varicella pneumonia?

Answers

Case 83

Varicella-Zoster (Chickenpox)

1 Varicella-zoster (chickenpox).

2 Approximately 15%.

4 Diffuse, discrete pulmonary calcifications.

Reference

Müller NL, Silva CI: Viruses. In: Müller NL, Silva CI, Eds. Imaging of the Chest. Philadelphia, Saunders, 2008, pp 402-404.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, pp 96, 99.

Comment

The chest radiograph demonstrates a diffuse distribution of poorly defined small lung nodules, some of which have coalesced to form areas of consolidation. The appearance is typical of varicella-zoster (chickenpox) pneumonia. Characteristic CT findings (not shown) include 1- to 10-mm nodules diffusely distributed throughout the lungs. Less common findings at CT include nodules with surrounding ground-glass halos, patchy ground-glass opacities, and coalescing nodules.

The varicella-zoster virus is seen in two clinical forms: chickenpox (varicella) and zoster (shingles). Chickenpox represents the primary form of the virus and usually presents as disseminated disease in previously uninfected individuals. Conversely, zoster represents reactivation of a latent virus and typically manifests as a unilateral dermatologic skin eruption. Although either form of the virus may be associated with pneumonia, the majority of cases occur in association with chickenpox.

The overall incidence of pneumonia in adults with chickenpox ranges from 5% to 50%. Predisposing factors include leukemia, lymphoma, immunodeficiency, and pregnancy. Both the incidence and the severity of varicella pneumonia are significantly higher in pregnant women than in the general population.

Acute chickenpox pneumonia is most common in adult patients with severe cutaneous disease. Affected patients typically present 2 or 3 days following the appearance of a skin eruption with symptoms of cough, dyspnea, tachypnea, and pleuritic chest pain.

Acute chickenpox pneumonia is associated with a mortality rate as high as 10%. In patients who survive the infection, clinical improvement usually precedes radiographic clearing by several weeks. A characteristic radiologic finding in patients with healed varicella pneumonia is the presence of diffuse discrete pulmonary calcifications.

Case 84

1 Name at least four causes of a unilateral, enlarged apical cap.

2 What is the term used to describe a primary lung cancer that arises at the apex of the lung?

3 Regarding extrapleural apical lesions, are their margins usually smooth or irregular?

4 This patient presented with a palpable right-sided neck mass. Name two possible causes for the enlarged apical cap in this case.

Answers

Case 84

Apical Cap Secondary to Extrapleural Abscess Extending From the Neck

1 Primary lung cancer, lymphoma extending from the neck or mediastinum, extrapleural hematoma related to injury, extrapleural abscess extending from the neck, and radiation fibrosis.

2 Superior sulcus tumor.

4 Extrapleural extension of neck abscess and lymphoma.

Reference

McLoud TC, Isler RJ, Novelline RA, et al: The apical cap. AJR Am J Roentgenol 137:299-306, 1981.

Cross-Reference

Comment

The term apical cap has been used to describe the presence of an opacity located in the extreme apex of the lung on chest radiographs. On chest radiographs of normal, asymptomatic patients, you will often observe the apical cap as an irregular opacity located over the apex of the lung, usually measuring less than 5 mm in diameter. The lower margin is usually sharply marginated but often demonstrates an undulating border. Apical caps are thought to represent the result of nonspecific subpleural scarring and apical pleural thickening, and they are usually of no clinical significance. The prevalence of apical caps increases with age.

A variety of entities may result in an enlarged apical cap. The various causes of a unilateral enlarged cap have been listed in Answer 1. With regard to bilaterally enlarged apical caps, they may be associated with radiation fibrosis (e.g., for Hodgkin’s disease), mediastinal lipomatosis, and vascular abnormalities such as coarctation of the aorta.

In this case, the presence of a smoothly marginated enlarged right apical cap is due to extension of a neck abscess into the lung apex. Because of the continuity of the fascial planes of the neck with the thoracic apical region, infectious processes originating in the neck may extend into the area of the lung apex, within the extrapleural space. The apical cap in such cases is smoothly marginated, reflecting the extrapleural location. Lymphoma is an additional important consideration in this case. In patients with lymphoma, an apical cap may be produced by extension of lymphadenopathy from the neck or by enlargement of lymph nodes along the apical pleura.

Case 85

1 What is the etiology of the abnormal low-attenuation areas present in both lungs on these HRCT images?

2 What types of emphysema are evident in this case?

3 What type of emphysema is most closely associated with cigarette smoking?

4 What portion of the lungs is most commonly affected by this type of emphysema?

Answers

Case 85

Emphysema

2 Centrilobular and paraseptal.

3 Centrilobular.

Reference

Kazerooni EA, Whyte RI, Flint A, Martinez FJ: Imaging of emphysema and lung volume reduction surgery. Radiographics 17:1023-1036, 1997.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, pp 242-248.

Comment

The HRCT image and magnified view of the left lung demonstrate multiple foci of low attenuation, consistent with emphysema. Note the absence of definable walls for most of the areas of abnormal low attenuation.

Features of both centrilobular and paraseptal emphysema are present. Centrilobular emphysema is characterized by multiple small, round foci of abnormally low attenuation, typically without visible walls, that are scattered throughout the lung parenchyma. Paraseptal emphysema is characterized by its location within the subpleural regions and adjacent to the interlobar fissures. Foci of paraseptal emphysema often have thin visible walls that correspond to interlobular septa. In this case, paraseptal emphysema is best demonstrated adjacent to the anterior pleural surfaces. When larger than a centimeter in size, foci of paraseptal emphysema and/or confluent areas of centrilobular emphysema, are most appropriately referred to as “bullae.”

HRCT of the chest is highly sensitive and specific for the diagnosis of emphysema. It is particularly helpful for assessing the severity and distribution of emphysema in patients who are potential candidates for lung volume reduction surgery (LVRS). LVRS is a procedure that involves the resection of “target areas” of severely emphysematous lung. Such regions contribute little to pulmonary function and negatively alter respiratory mechanics. LVRS usually involves bilateral wedge resection procedures performed via a median sternotomy.

Improved pulmonary function following LVRS is thought to be due to several factors, including improved elastic recoil of the lungs, correction of mismatches, and improved mechanics of breathing. Patients are selected for the procedure based on a variety of clinical and imaging parameters. With regard to imaging features, preliminary data suggest that patients with a heterogeneous distribution of emphysema with an upper lobe predominance are most likely to benefit from this procedure.

Case 86

1 This patient has a history of lymphoma and is being treated with bleomycin. What is the most likely cause for the interstitial opacities observed in the first and second figures?

2 Approximately what percentage of patients receiving bleomycin develop pulmonary toxicity?

3 Does simultaneous chest radiation therapy increase or decrease the risk of bleomycin pulmonary toxicity?

4 Would you expect this patient’s diffusing capacity of carbon monoxide (DLCO) to be increased or decreased?

Answers

Case 86

Bleomycin Drug Toxicity

1 Bleomycin pulmonary toxicity.

2 Approximately 4%.

Reference

Rossi SE, Erasmus JJ, McAdams HP, et al: Pulmonary drug toxicity: radiologic and pathologic manifestations. Radiographics 20:1245-1259, 2000.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, pp 236-237.

Comment

The chest radiograph in the first figure reveals the presence of reticular opacities within the peripheral and basilar portions of the lung parenchyma. The CT images in the second and third figures demonstrate thickened septal lines, irregular linear opacities, ground-glass opacities, and several tiny lung nodules in a subpleural and basilar predominance.

Bleomycin is an antitumor agent that is used to treat lymphomas, testicular carcinomas, and certain squamous cell carcinomas. Pulmonary toxicity occurs in approximately 4% of patients and is the principal dose-limiting factor for this agent. Pulmonary fibrosis is the most serious pulmonary complication, but an acute hypersensitivity reaction occurs rarely.

Affected patients typically present with an insidious onset of dyspnea, nonproductive cough, and occasional fever. Pulmonary function tests reveal a decreased DLCO, a sensitive measure for early bleomycin lung injury.

Chest radiographs may be normal or may demonstrate reticular opacities in a basilar and subpleural distribution, similar to those observed in idiopathic pulmonary fibrosis. CT (especially HRCT) is more sensitive that conventional radiographs for detecting interstitial abnormalities and may reveal characteristic findings even when the chest radiograph is normal. Pulmonary nodules are an uncommon manifestation of bleomycin toxicity and usually represent drug-induced COP (cryptogenic organizing pneumonia). Nodules may vary in size from 5 mm to 3 cm and are usually subpleural in distribution.

Early detection is important because prompt discontinuation of bleomycin may result in improved pulmonary function and healing of pulmonary damage in patients with early stages of disease. In patients with more advanced disease, the prognosis is variable. Although some patients respond to steroids, others develop progressive fibrosis that may lead to respiratory failure and death.

Case 87

1 In an HIV-positive patient, which fungal infection is most likely to present with pulmonary nodules, pleural effusion, and lymph node enlargement?

2 Are pleural effusions and thoracic lymph node enlargement more commonly observed in immunocompetent or immunosuppressed patients with cryptococcal pulmonary infection?

3 What organ system is most commonly affected by this organism?

4 What other organ systems are commonly involved in disseminated cryptococcal infection?

Answers

Case 87

AIDS Cryptococcal Infection

1 Cryptococcus.

2 Immunosuppressed.

3 Central nervous system (meningitis).

4 Bone and skin.

Reference

Avriam G, Fishman JE, Boiselle PM: Thoracic infections in human immunodeficiency virus/acquired immune deficiency syndrome. Semin Roentgenol 42:23-36, 2007.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, p 128.

Comment

The CT images in this case demonstrate several small pulmonary nodules with associated left hilar and subcarinal lymph node enlargement and a small left pleural effusion. There are a variety of causes of lung nodules in patients with AIDS, including infectious etiologies (fungal, mycobacterial, septic infarcts) and neoplasms (KS, lymphoma).

Prior to the AIDS epidemic and the advent of immunosuppressive therapies, most cryptococcal infections occurred in immunocompetent hosts. It is estimated that approximately 70% of such infections now occur in immunosuppressed patients. In immunocompetent hosts, the infection is usually localized to the lung. In contrast, in immunosuppressed patients, dissemination to the central nervous system and skin is common. Pulmonary symptoms are uncommon in both groups. However, immunosuppressed patients with disseminated disease frequently present with symptoms related to the central nervous system or skeletal system.

A variety of imaging features are associated with this infection. Common manifestations in both immunosuppressed and immunocompetent hosts include solitary or multiple pulmonary nodules and masses and segmental or lobar consolidation. Other features, including diffuse reticulonodular opacities, cavitating nodules or masses, pleural effusion, and mediastinal and hilar lymph node enlargement, are more commonly observed in immunosuppressed patients than in normal hosts.

Case 88

1 Transthoracic biopsy of the lung mass shown in the figures revealed NSCLC. Is the presence of an enlarged aortopulmonary window lymph node sufficient proof of metastatic nodal disease?

2 Based on the TNM classification system for NSCLC, if this node is proved malignant, what would be the N status of the patient?

3 Does this nodal status preclude surgical resection?

4 What is the significance of contralateral nodal disease in patients with NSCLC?

Answers

Case 88

Lung Cancer With N2 Nodal Disease

4 It precludes surgical resection.

References

Sharma A, Fidias P, Hayman LA, et al: Patterns of lymphadenopathy in thoracic malignancies. Radiographics 24:419-434, 2004.

Kligerman S, Abbott G: A radiologic review of the new TNM classification for lung cancer. AJR Am J Roentgenol 194:562-573, 2010.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, pp 263-268.

Comment

In patients with NSCLC, the nodal status provides important information for determining prognosis and planning appropriate therapy. Although no changes are planned for the N designation in the seventh edition of the TNM classification system, a new nodal chart has been created that places lymph nodes into seven specific zones: supraclavicular, upper, aorticopulmonary, subcarinal, lower, hilar-interlobar, and peripheral.

According to the TNM classification system, nodal involvement is graded from N0 to N3 as follows:

N0 = no demonstrable metastases to regional lymph nodes.

N1 = metastasis to lymph nodes in the ipsilateral peripheral, or hilar-interlobar regions.

N2 = metastasis to ipsilateral mediastinal nodes (upper, aorticopulmonary, lower or subcarinal).

N3 = metastasis to any supraclavicular nodes, or to contralateral mediastinal (upper, aorticopulmonary, lower), hilar-interlobar, or peripheral regions.

CT and MRI play an important but limited role in the assessment of nodal status in patients with bronchogenic carcinoma. These imaging modalities rely primarily on anatomic features of lymph nodes, most notably lymph node size (short axis greater than 1 cm diameter is generally considered abnormal). This strategy is associated with sensitivities in the range of 60% to 79% and specificities in the range of 60% to 80%. Thus, for staging purposes, enlarged nodes must be evaluated by biopsy. The primary role of these modalities is to identify the location of enlarged nodes. This information allows appropriate biopsy procedures to be planned.

In recent years, FDG-PET imaging has been shown to be superior to CT and MRI in the assessment of mediastinal lymph nodes. This technique relies on physiologic (glucose metabolism) rather than anatomic features to identify abnormal lymph nodes. Thus, it has the potential to identify neoplastic involvement within small nodes and to differentiate enlarged, hyperplastic nodes from neoplastic nodes.

Case 89

1 What is the most common cause of superior vena cava (SVC) syndrome?

2 Name at least one common benign cause of SVC syndrome.

3 Name at least two mechanisms by which the SVC may become obstructed.

4 What are the typical clinical symptoms of a patient with SVC obstruction?

Answers

Case 89

SVC Syndrome

1 Malignancy—lung cancer.

2 Long-term intravenous devices; fibrosing mediastinitis.

3 Extrinsic compression, direct invasion, and intraluminal thrombus.

4 Edema of the face, neck, upper extremities, and thorax; headache; visual disturbances; and reduced level of consciousness.

Reference

Eran S, Karaman A, Okur A: The superior vena cava syndrome caused by malignant disease: imaging with multidetector row CT. Eur J Radiol 59:93-103, 2006.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, p 262.

Comment

The SVC syndrome is caused by obstruction of the SVC by either external compression, intraluminal thrombosis, neoplastic infiltration, or a combination of these processes. The vast majority of cases occur secondary to a neoplastic process, most commonly bronchogenic carcinoma (especially small cell carcinoma). Lymphoma and metastatic carcinoma are additional malignant causes. There are a variety of benign etiologies, including long-term intravenous devices (e.g., Hickman catheters and permanent pacemakers) and fibrosing mediastinitis (e.g., histoplasmosis).

Chest radiographs frequently demonstrate a mass in the right paratracheal region, which may be accompanied by distention of the azygos vein. In the setting of fibrosing mediastinitis, the right paratracheal mass is frequently calcified. In patients who develop thrombosis of the SVC owing to an indwelling catheter, lateral displacement of the catheter may be seen. The diagnosis of SVC obstruction can be confirmed by CT or MRI. On CT, the diagnosis is based on decreased or absent contrast opacification of the SVC in conjunction with opacification of collateral vessels. Both findings are necessary to make a reliable diagnosis. Contrast-enhanced MDCT with multiplanar reformation and three-dimensional reconstructions is highly accurate at detecting the presence and level of SVC obstruction. It is also valuable for helping to determine the cause of obstruction and for delineating the collateral venous circulation.

When you observe collateral venous vessels, you should always search for a central venous obstruction.

Case 90

1 What is the term used to describe the presence of periosteal reaction in association with pulmonary disease?

2 Are benign or malignant disorders more commonly associated with this process?

3 When this process occurs in association with a pulmonary malignancy, what is the usual response of the periosteal reaction following pulmonary neoplasm resection?

4 Is this skeletal process typically symptomatic?

Answers

Case 90

Hypertrophic Pulmonary Osteoarthropathy

1 Hypertrophic pulmonary osteoarthropathy (HPOA).

4 Yes—it is usually associated with pain, swelling, and stiffness.

Reference

Love C, Din AS, Tomas MB, et al: Radionuclide bone imaging: an illustrative review. Radiographics 23:341-358, 2003.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, pp 256-257.

Comment

The radiographs of the right ankle shown in the first figure reveal the presence of smoothly marginated periosteal reaction along the shafts of the distal tibia and fibula. A similar appearance was present in radiographs of the remaining extremities (not shown).

The term HPOA is used to describe the association between this skeletal condition and visceral disease within an organ supplied by the vagal or glossopharyngeal nerves. Although there are a variety of pulmonary and extrapulmonary causes of this condition, malignant pulmonary neoplasms account for the vast majority (90%) of cases. Because of this strong association, you should always recommend that a patient with evidence of HPOA undergo a chest radiograph to assess for pulmonary neoplasm or other causes of pulmonary disease. Note the large central neoplasm on the chest radiograph of this patient in the second figure. Common nonneoplastic pulmonary conditions include cystic fibrosis and idiopathic pulmonary fibrosis. Localized fibrous lesions of the pleura are also frequently associated with this condition.

The underlying mechanism of this condition is poorly understood, but it is believed to be due to an osteogenic effect exerted by a cytokine. Vascular endothelial growth factor (VEGF) has recently been suggested as a possible cytokine for inciting this reaction. Interestingly, following resection of an associated thoracic malignancy, HPOA usually disappears.

Case 91

1 Does this patient have an acute pulmonary embolus?

2 What is the cause of the focal decrease in caliber of the descending left pulmonary artery?

3 In patients with sarcoidosis, how frequently do enlarged nodes result in compression of pulmonary arteries?

4 What vascular structure appears abnormally dilated in the first figure?

Answers

Case 91

Extrinsic Compression of Pulmonary Arteries (Sarcoid)

2 Extrinsic compression by adjacent nodal tissue.

4 Main pulmonary artery.

Reference

Hennebicque AS, Nunes H, Brillet PY, et al: CT findings in severe thoracic sarcoidosis. Eur Radiol 15:23-30, 2005.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, pp 334, 335.

Comment

The CT pulmonary angiogram images in the first (axial) and second (coronal reformation) figures reveal extrinsic narrowing of the descending left pulmonary artery and superior segment right lower lobe pulmonary artery by adjacent nodal tissue.

This patient has a history of sarcoidosis. Occasionally, enlarged nodes in patients with sarcoidosis are sufficiently large to compress the bronchi. Rarely, enlarged nodes may result in narrowing of pulmonary arteries, as demonstrated in this case. Massively enlarged right paratracheal nodes have been reported to obstruct the superior vena cava.

In patients with sarcoidosis, pulmonary arterial hypertension is usually secondary to end-stage pulmonary fibrosis. However, it may rarely occur secondary to extrinsic compression of major pulmonary arteries by enlarged lymph nodes or by compression and obliteration of small arterioles by adjacent granulomas.

When interpreting CT pulmonary angiograms, it is important to distinguish pulmonary emboli from extrinsic abnormalities such as lymph nodes. Note the absence of intrinsic filling defects within the pulmonary vasculature in this case. One additional distinguishing feature is the size of the pulmonary arteries. In the setting of an acute pulmonary embolus, the affected vessel is often dilated. In contrast, when extrinsically compressed, the vessel will be abnormally narrowed. Extrinsic compression may be more difficult to distinguish from chronic pulmonary emboli, which result in mural rather than central pulmonary artery filling defects. Recognition that the abnormal soft tissue attenuation material is extrinsic rather than intrinsic to the vessel allows one to exclude chronic pulmonary embolus. Although this distinction can usually be made readily on conventional axial images (as is true in this case), supplemental multiplanar reformatted images are helpful for difficult cases.

Case 92

1 This patient has a history of hemophilia. What is the likely cause for this posterior chest wall mass?

2 What does the high-attenuation component of the mass represent on this unenhanced CT scan study?

3 Name at least two potential complications of intramuscular hemorrhage.

4 How is hemophilia genetically transmitted?

Answers

Case 92

Chest Wall Hematoma in Hemophilia

2 Acute hemorrhage.

3 Joint contractures, ischemic myopathy, neuropathy, pressure necrosis of adjacent bone, and pseudotumor formation.

4 X-linked recessive; thus, hemophilia is transmitted by females but primarily affects males.

Reference

Park JS, Ryu KN: Hemophilic pseudotumor involving the musculoskeletal system: spectrum of radiologic findings. AJR Am J Roentgenol 183:55-61, 2004.

Cross-Reference

Comment

The CT images reveal a large, well-marginated, heterogeneous posterior chest wall mass with its epicenter in the left paraspinal musculature. The high attenuation of this mass on an unenhanced CT is consistent with the diagnosis of acute intramuscular hematoma, a known complication of hemophilia.

Hemophilia refers to a disorder characterized by a coagulation defect caused by a deficiency of clotting factor. Repetitive bleeding into the musculoskeletal system is the most common complication of this condition. The joint spaces are the most common site of spontaneous bleeding. Hemarthrosis is frequently complicated by arthritis. The soft tissues, particularly large muscle groups, are also a relatively common site of hemorrhage. The most commonly affected muscle groups are the iliopsoas, quadriceps, and gastrocnemius. If bleeding into the hematoma is replaced by fibrous tissue, a permanent contracture may develop. Encapsulation of a hematoma may result in the formation of a pseudotumor.

Cross-sectional imaging studies can be helpful for identifying the site and extent of intramuscular hematomas in patients with hemophilia. Because of its relative low cost and lack of ionizing radiation, ultrasonography is usually the preferred modality for this purpose. In patients with large hematomas, CT and MRI are occasionally helpful for determining the extent of hemorrhage, estimating the age of hemorrhage, and demonstrating the effect of the hemorrhage on adjacent organs.

Case 93

1 What feature suggests a benign, nonaggressive etiology of this rib lesion?

2 Name at least two likely causes of this rib lesion.

3 Name an entity that may be associated with chronic infiltrative lung disease and lucent bone lesions.

4 Name at least three primary neoplasms that are frequently associated with lytic bone metastases.

Answers

Case 93

Enchondroma

1 Well-circumscribed, sclerotic margins.

2 Fibrous dysplasia, aneurysmal bone cyst, enchondroma, nonossifying fibroma, and Langerhans cell histiocytosis (LCH).

3 LCH (although pulmonary involvement is usually not accompanied by bone lesions).

4 Lung, breast (lytic or blastic), kidney, and thyroid.

Reference

Guttentag AR, Salwen JK: Keep your eyes on the ribs: the spectrum of normal variants and diseases that involve the ribs. Radiographics 19:1125-1142, 1999.

Cross-Reference

Comment

The coned-down chest radiograph in the first figure and the coned-down rib radiograph in the second figure reveal a well-circumscribed, expansile, lucent lesion in the left fourth anterior rib with sclerotic margins. The well-defined, sclerotic margins suggest a nonaggressive rather than an aggressive (e.g., neoplasm, infection) etiology. In contrast, aggressive lucent lesions are typically characterized by poorly defined margins.

There are a variety of causes of benign lucent rib lesions. Careful inspection of this lesion reveals subtle foci of calcification within the lucent center of this lesion. This finding suggests a cartilaginous lesion such as enchondroma. In approximately 50% of cases, such lesions demonstrate calcification, which is usually manifested by punctate foci or rings and arcs of calcification. Enchondromas are asymptomatic unless complicated by pathologic fracture or rare malignant degeneration to chondrosarcoma. The latter should be suspected when a patient with an enchondroma presents with pain in the absence of trauma.

The most common nonneoplastic lesion of the thoracic skeleton is fibrous dysplasia. In patients with this disorder, the rib lesion is usually monostotic and asymptomatic. However, patients may present with symptoms if the lesion is complicated by pathologic fracture. In cases of polyostotic fibrous dysplasia, there is usually a unilateral predominance. Rarely, the degree of thoracic involvement is sufficient to result in progressive restrictive lung disease, pulmonary hypertension, and cor pulmonale. McCune-Albright syndrome refers to the presence of polyostotic fibrous dysplasia accompanied by café au lait skin lesions and precocious puberty.

Case 94

1 What structure is delineated between the arrows on the lateral chest radiograph in the second figure?

2 Is this abnormally widened?

3 What do the lucencies on either side of this structure represent?

4 What descriptor is used to characterize the typical appearance of the cardiac contour in the setting of a pericardial effusion?

Answers

Case 94

Pericardial Effusion

2 Yes—it is widened by the presence of pericardial effusion.

4 Water bottle or flask shape.

Reference

Cardiac Radiology: THE REQUISITES, pp 265-270.

Cross-Reference

Comment

The chest radiograph in the first figure demonstrates an enlarged cardiac contour, with a globular configuration. The lateral radiograph in the second figure demonstrates a positive epicardial fat pad sign (EFPS), also referred to as the double-lucency sign. This sign refers to widening (greater than 4 mm) of the soft tissue opacity of the pericardium between the lucent stripes (arrows) that represent fat located anterior and posterior (epicardial) to the pericardium. These lucent stripes are demarcated by paired arrows on the coned-down image of the lateral chest radiograph in the third figure. The EFPS has a relatively low sensitivity but a high specificity for detecting pericardial effusion.

Chest radiography is associated with a relatively poor sensitivity for detecting pericardial effusions. It has been estimated that approximately 200 ml of pericardial fluid must be present to reliably make the diagnosis radiographically. In contrast, echocardiography is highly sensitive for detecting pericardial effusion and is the study of choice for screening patients with suspected pericardial effusion. MRI may be helpful for characterizing complex pericardial fluid collections.

There are a variety of causes of pericardial effusion, including infection, trauma, radiation therapy, collagen vascular diseases, metabolic disorders, and neoplasms. The most common cause is myocardial infarction with left ventricular failure. Dressler’s syndrome refers to the development of pericardial and pleural effusions 2 to 10 weeks following myocardial infarction. Such effusions can be hemorrhagic, particularly in patients who have received anticoagulation therapy. The patient in this case developed pericardial and pleural effusions following myocardial infarction.

Case 95

1 Is this a case of cystic lung disease or bronchiectasis?

2 How can you make this distinction?

3 What are the three classifications of bronchiectasis (Reid classification)?

4 Name at least three congenital or developmental disorders associated with bronchiectasis.

Answers

Case 95

Bronchiectasis

1 Bronchiectasis.

2 Many of the cystic spaces are connected, several run parallel to adjacent vessels (“signet ring sign”), and several have air-fluid levels.

3 Cylindrical, varicose, and cystic (saccular).

4 Williams-Campbell syndrome, cystic fibrosis, primary hypogammaglobulinemia, “yellow nail” syndrome, immotile cilia syndrome (Kartagener’s syndrome), Young’s syndrome, and Mounier-Kuhn syndrome.

Reference

Javidan-Nejad C, Bhalla S: Bronchiectasis. Radiol Clin North Am 47:289-306, 2009.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, pp 314-318.

Comment

The term bronchiectasis refers to abnormal, irreversible dilation of the bronchi. The definitive pathologic description of bronchiectasis was reported by Reid and is based on the morphology of the bronchi and the number of bronchial subdivisions that are present. In cylindrical bronchiectasis, the bronchi are minimally dilated and have a straight, regular contour. The average number of bronchial subdivisions from the hilum to the lung periphery is 16 (17 to 20 is normal). In varicose bronchiectasis, the bronchi demonstrate a beaded appearance with sequential dilation and constriction. The average number of bronchial divisions is 8. In cystic bronchiectasis, the bronchi have a ballooned appearance. The average number of bronchial divisions is only 4.

You can distinguish bronchiectasis from cystic lung disease by using the following criteria. First, when dilated bronchi course perpendicular to the scanning plane, you will always see a pulmonary artery running adjacent to it (signet ring sign). In contrast, true lung cysts, such as those associated with LAM, are located randomly in the lung parenchyma. Second, when dilated bronchi course parallel to the scanning plane, you will observe that the cystic spaces connect with one another. This feature is nicely demonstrated in this case. Finally, cystic bronchiectasis is often associated with fluid levels, a finding that is not generally observed in cystic lung disease.

Case 96

1 Name the structure that is likely responsible for displacement of the azygoesophageal contour (arrows) in this patient.

2 Why does this appear as a stripe rather than an interface?

3 What imaging study would be most helpful for further evaluation of this finding?

4 Name at least two causes of thoracic esophageal dysmotility.

Answers

Case 96

Esophageal Dysmotility (Achalasia)

2 The esophagus is distended with air.

3 Barium swallow.

4 Progressive systemic sclerosis (scleroderma), achalasia, Chagas’ disease, systemic diseases (e.g., amyloidosis), and drugs (e.g., anticholinergics).

Reference

Whitten CR, Khan S, Munneke GJ, Grubnic S: A diagnostic approach to mediastinal abnormalities. Radiographics 27:657-671, 2007.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, pp 364-365, 366.

Comment

The azygoesophageal interface is produced by the juxtaposition of aerated lung in the right lower lobe and the soft tissue opacity of the right lateral margin of the azygos vein and/or esophagus. On normal chest radiographs, you will observe the azygoesophageal interface beginning at the level of the azygos arch and extending inferiorly to the level of the diaphragm. It normally produces a concave slope as it curves slightly toward the left. Abnormalities of either the azygos vein (e.g., azygos continuation of the inferior vena cava) or the esophagus (e.g., achalasia) may result in rightward displacement of this interface. Subcarinal masses such as bronchogenic cysts and lymph node enlargement may also result in focal rightward displacement of the azygoesophageal interface, usually producing a rightward convexity in the subcarinal region.

The chest radiograph reveals diffuse, rightward displacement of the azygoesophageal contour, which appears as a stripe rather than an interface. When the azygoesophageal contour is displaced by an air-filled, distended esophagus, you will observe a stripe rather than an interface. This patient has a history of achalasia. In most patients with this disorder, the esophagus contains a large amount of retained secretions. Therefore, you will usually see a displaced azygoesophageal interface rather than a stripe. Retained secretions may also result in a discrete air-fluid level within the distended esophagus.

Case 97

1 This patient reports recent travel to the southwestern United States. What is the most likely infectious etiology of this cavity?

2 Where else is this organism endemic?

3 Are cavities associated with the initial pneumonic form or the chronic form of this infection?

4 What is the typical pattern associated with disseminated coccidioidomycosis infection?

Answers

Case 97

Cavity Due to Coccidioidomycosis

1 Coccidioidomycosis.

2 Central and South America and northern Mexico.

4 Multiple, small nodules.

Reference

Lindell RM, Hartman TE: Fungal infections. In: Müller NL, Silva CI, Eds. Imaging of the Chest, Philadelphia, Saunders, 2008, pp 362-365.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, p 110.

Comment

Coccidioidomycosis infection is caused by inhalation of infected spores of Coccidioides immitis, a soil inhabitant that is endemic to desert areas. Although most individuals are asymptomatic following exposure, some will experience a mild, flulike illness.

Radiographic findings vary depending on the stage of infection. Following initial inhalation of the spores, there is a local pneumonic response, which is characterized radiographically as an area of consolidation. Such consolidation usually involves less than an entire lobe, is often located in the lower lobes, and usually resolves spontaneously without therapy.

Chronic pulmonary coccidioidomycosis is characterized radiographically by solitary or multiple pulmonary nodules and cavities. Such cavities, as demonstrated in this case, may have variable wall thickness and are usually radiologically indistinguishable from other causes of cavitary lesions. In a minority (10% to 15%) of cases, coccidioidomycosis is associated with characteristic thin-walled (“grapeskin”) cavities. Such cavities may rapidly change in size, presumably due to a check-valve communication with the bronchial tree.

Disseminated coccidioidomycosis is rare; it presents radiographically as multiple nodules. The nodules usually range in size from 5 mm to 1 cm in diameter, but smaller miliary nodules may be observed in some cases. The course of disseminated coccidioidomycosis is variable: it may be chronic and insidious or rapidly fatal. The latter usually occurs in patients who are immunocompromised.

Similar to other infections, coccidiomycosis may cause a false-positive result on FDG-PET studies. This may occur in the acute or chronic phase of infection.

Case 98

1 This patient’s pulmonary venous wedge pressure was elevated. What is the most likely cause for these chest HRCT findings?

2 What chest radiographic finding correlates with the HRCT finding of thickened interlobular septa?

3 Define ground-glass opacity.

4 Name two technical features that are necessary components of HRCT imaging.

Answers

Case 98

Hydrostatic Pulmonary Edema

1 Hydrostatic pulmonary edema.

2 Kerley (septal) lines.

3 Hazy increased opacity of lungs with preservation of bronchial and vascular margin visibility.

4 Thin collimation (1- to 2-mm) and high spatial frequency reconstruction algorithm.

Reference

Storto ML, Kee ST, Golden JA, Webb WR: Hydrostatic pulmonary edema: high-resolution CT findings. AJR Am J Roentgenol 165:817-820, 1995.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, pp 330-332.

Comment

Although a diagnosis of congestive heart failure is usually made on the basis of typical clinical and radiographic findings, occasionally patients with unsuspected congestive heart failure are imaged with chest HRCT in search of a cause of dyspnea. Hydrostatic edema is also an occasional incidental finding in patients who are being scanned for other purposes. Thus, it is important to be aware of the typical HRCT features of hydrostatic edema.

On HRCT of patients with hydrostatic edema, you may observe a combination of ground-glass opacity, smoothly thickened septal lines, peribronchovascular interstitial thickening, increased vascular caliber, and thickened fissures. Small pleural effusions, often right-sided, are also frequently observed. There is an absence of signs of fibrosis such as honeycombing, traction bronchiectasis, and architectural distortion. Interestingly, patients with acute congestive heart failure have also been reported to demonstrate occasionally enlarged mediastinal lymph nodes and haziness of the mediastinal fat.

Correlation between imaging findings and clinical data is usually sufficient to confirm the diagnosis. When the diagnosis is in doubt clinically, a follow-up study after diuresis can occasionally be helpful to confirm resolution of abnormalities and to exclude chronic infiltrative lung disease.

Case 99

1 In this patient with a history of breast cancer, what is the most likely cause for the lobulated retrosternal opacity seen on the lateral chest radiograph in the second figure?

2 What other neoplastic process commonly involves this nodal group?

3 Does a normal chest radiograph exclude enlarged nodes at this site?

4 Name the most common site of enlarged nodes in patients with breast cancer.

Answers

Case 99

Internal Mammary Lymph Node Enlargement

1 Enlarged internal mammary lymph nodes.

Reference

Sharma A, Fidias P, Hayman LA, et al: Patterns of lymphadenopathy in thoracic malignancies. Radiographics 24:419-434, 2004.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, pp 373-374.

Comment

The serial lateral chest radiographs reveal interval development of a lobulated opacity in the retrosternal region. In a patient with a history of breast cancer, the most likely etiology is enlarged internal mammary lymph nodes, a common site of metastatic disease in such patients. The lymphatics that drain the medial portion of the breasts enter into the internal mammary lymph nodes. Involvement of internal mammary lymph nodes has prognostic significance and influences therapy decisions.

Enlarged internal mammary nodes are generally visible on chest radiographs only when they are considerably enlarged. On a posteroanterior (PA) chest radiograph of a patient with enlarged internal mammary nodes, you may observe a focal parasternal opacity, which is usually seen at the level of the first three intercostal spaces and less frequently at the fourth or fifth level. On a lateral radiograph, you may observe a lobulated retrosternal opacity, as demonstrated in this case. Most often, the opacity is observed at a more superior level than is shown in this case.

A lobulated retrosternal opacity may also be observed in patients with dilated internal mammary vessels. For example, coarctation of the aorta is associated with collateral internal mammary arteries and SVC obstruction is associated with collateral internal mammary veins. The former is associated with a characteristic appearance of the aorta and evidence of rib notching, and the latter is usually associated with a large mass in the right paratracheal region.

Case 100

1 The figures are CT images of two different patients undergoing transthoracic needle biopsy (TTNB) procedures. Which patient is least likely to experience a pneumothorax from this procedure? Why?

2 What is the sensitivity of TTNB for malignant nodules?

3 Name at least three complications of TTNB.

4 How can you improve the yield of TTNB for diagnosing benign lesions?

Answers

Case 100

CT-guided TTNB Procedure

1 The patient in the first figure, because the needle does not traverse aerated lung.

2 Greater than 90%.

3 Pneumothorax (20% to 30%); chest tube (5% to 15%); hemoptysis (1% to 10%); seeding of biopsy track; and air embolism.

4 Use a cutting core biopsy needle that provides a histologic specimen.

Reference

Boiselle PM, Shepard JA, Mark EJ, et al: Routine addition of an automated biopsy device to fine-needle aspiration of the lung: a prospective assessment. AJR Am J Roentgenol 169:661-666, 1997.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, pp 400-406.

Comment

The CT images demonstrate TTNB procedures of two separate patients. Note that the peripheral mass in the first figure does not require the biopsy needle to traverse aerated lung. Such lesions are associated with a very low pneumothorax rate.

With regard to planning a TTNB procedure, you should first obtain a prebiopsy CT scan. The shortest, most vertical route should be chosen, and the path of the needle should avoid interlobar fissures, pulmonary vessels, bullae, and areas of severe emphysema.

TTNB is a relatively safe and accurate procedure for obtaining biopsy specimens of lung nodules and masses. The sensitivity for malignant nodules is greater than 90%, and the accuracy for differentiating among various cell types of lung cancer is approximately 80%. A major limitation of TTNB using fine-needle aspiration is a relatively low sensitivity (10% to 40%) for making a specific benign diagnosis. However, this ability can be significantly improved by using core needle biopsy devices. Such devices provide histologic specimens that improve the accuracy of diagnosing benign entities such as granulomas, hamartomas, and organizing pneumonia.

It is important to remember that a negative biopsy for malignancy is not diagnostic unless a specific benign diagnosis has been rendered. Indeed, about 30% of nonspecific negative biopsies prove to represent malignancy. Thus, when you receive a nonspecific negative biopsy, you should consider repeating the biopsy with a core biopsy device. A core biopsy device is also recommended for biopsy of lesions with a suspected diagnosis of lymphoma in order to provide sufficient tissue for classification of lymphoma.

Case 101

1 Name four disease entities associated with mucoid impaction and mucocele formation.

2 Name six congenital conditions that affect the bronchi.

3 Which anatomic structures enable collateral air drift to occur in the lungs?

4 Name four possible etiologies of a tubular opacity on imaging studies.

Answers

Case 101

Bronchial Atresia

1 Allergic bronchopulmonary aspergillosis (ABPA), obstructing endobronchial tumor, congenital bronchial atresia (CBA), cystic fibrosis.

2 Bronchial (pulmonary) isomerism syndrome, bronchial atresia, congenital bronchiectasis (e.g., cystic fibrosis, Williams-Campbell syndrome), supernumerary bronchus, pig bronchus, cardiac bronchus.

3 Interalveolar pores of Kohn and the canals of Lambert.

4 AVM, partial anomalous pulmonary venous return (PAPVR), pulmonary varix, mucoid impaction.

Reference

Kinsella D, Sissons G, Williams MP: The radiological imaging of bronchial atresia. Br J Radiol 65:681-685, 1992.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, pp 60-63.

Comment

CBA is a rare and benign condition characterized by focal atresia of a segmental, subsegmental, or lobar bronchus. The airways distal to the point of atresia are normal and form mucus, but the obstruction to proximal drainage causes accumulation of mucus distal to the point of atresia with resultant mucoid impaction and formation of a mucocele. An important associated feature is hyperinflation of the distal lung parenchyma through collateral air drift. CBA manifests radiologically as a round, ovoid, or branching structure associated with distal hyperinflation, but may be overlooked on the chest radiograph. Although its imaging features are characteristic, CBA is frequently misdiagnosed, often mistaken for an AVM. Because most cases of CBA do not require surgical resection, recognition of its characteristic imaging features is essential for conservative patient management.

The differential diagnosis of CBA includes other causes of mucoid impaction including ABPA, benign and malignant endobronchial tumors (carcinoid, lung cancer), cystic bronchiectasis related to previous pneumonia, and tuberculous bronchostenosis.

Case 102

1 Name three diseases that may manifest on CT as centrilobular ground-glass nodules.

2 What anatomic structures are located in the central core of the secondary pulmonary lobule?

3 Name seven pulmonary diseases associated with cigarette smoking.

4 Which type of immunologic reaction is associated with hypersensitivity pneumonitis?

Answers

Case 102

Hypersensitivity Pneumonitis

1 Subacute hypersensitivity pneumonitis (HP), respiratory bronchiolitis, respiratory bronchiolitis–interstitial lung disease (RB-ILD), PCP, pulmonary LCH.

2 Lobular bronchiole, pulmonary artery, and associated peribronchovascular lymphatics.

3 Emphysema, lung cancer, respiratory bronchiolitis, RB-ILD, desquamative interstitial pneumonia (DIP), PLCH, chronic bronchitis.

Reference

Kim KI, Kim CW, Lee MK, et al: Imaging of occupational lung disease. Radiographics 21:1371-1391, 2001.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, pp 230-233.

Comment

The presence of centrilobular ground-glass nodules on CT/HRCT should prompt consideration of the diagnosis of subacute HP. Affected patients typically present with dyspnea and chronic cough, and the clinical picture may be confused with other forms of interstitial lung disease. Often, the radiologist is the first member of the health care team to suggest the possibility of HP, and the clinical team may then investigate the patient’s environmental and occupation exposures to seek a causative antigen. Differential diagnostic considerations for centrilobular ground-glass nodules should include respiratory bronchiolitis, a disease that affects cigarette smokers, and in the proper clinical setting, atypical infection, including PCP. Centrilobular nodules in subacute HP may be of solid (soft tissue) and/or ground-glass attenuation and may be associated with patchy areas of ground-glass attenuation. The findings tend to predominate in the upper lung zones, and air trapping may be present on expiratory CT imaging. Treatment of subacute HP consists of removing the offending antigen from the patient’s environment. Chronic forms may require treatment with corticosteroids.

Case 103

1 What is the recommended follow-up (Fleischner Society guidelines) to evaluate this 4-mm solid nodule incidentally detected in a 48-year-old man with a 30-pack-year history of cigarette smoking?

2 How would the follow-up recommendations differ if the nodule were of ground-glass opacity?

3 What is the likelihood that an SPN larger than 20 mm is malignant?

4 What do the Fleischner Society guidelines recommend if a 20-mm nodule is detected in a patient with known underlying malignant disease?

Answers

Case 103

Solitary Pulmonary Nodule (SPN), 4 mm

1 CT follow-up at 12 months. If unchanged and of solid (soft tissue) attenuation, no further follow-up is necessary.

2 Nonsolid (ground-glass) or partly solid nodules may require longer follow-up to exclude an indolent adenocarcinoma.

4 The Fleischner guidelines do not apply to patients with known underlying malignant disease.

Reference

MacMahon H, Austin JH, Gamsu G, et al: Guidelines for management of small pulmonary nodules on CT scans: a statement from the Fleischner Society. Radiology 237:395-400, 2005.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, pp 284-286.

Comment

An SPN may represent a benign or malignant lesion. The probability that a nodule is malignant increases according to its size. The likelihood of malignancy in a nodule measuring less than 3 mm is only 0.2%; for nodules measuring 4 to 7 mm, the likelihood increases to 0.9%. Nodules measuring 8 to 20 mm and those measuring greater than 20 mm have a likelihood of malignancy of 18% and 50%, respectively.

More than 50% of all cigarette smokers older than 50 years have at least one pulmonary nodule detected on CT. Cigarette smokers are at greater risk to develop lethal lung cancers than nonsmokers; and their cancer risk increases in proportion to the duration and degree of their smoking. The likelihood of malignancy of an SPN also increases with patient age.

The Fleischner Society published a set of recommendations for the management of incidental solitary pulmonary nodules in 2005 (see Reference). These guidelines apply only to adult patients with nodules that are “incidental,” that is, are unrelated to known underlying disease. The guidelines also point out that previous studies (CT scans, chest radiographs) should be obtained, when possible, because they may demonstrate either stability or interval growth of the nodule in question.

Under the Fleischner Society guidelines, the recommended CT follow-up becomes more frequent with increasing nodule size. Furthermore, patients are categorized as “low-risk” (those with a minimal or absent history of smoking and/or other known risk factors) or “high-risk” (those with a history of smoking or of other known risk factors). For individuals in the low-risk category, the recommendations are as follows: nodule 4 mm or less: no follow-up needed; nodule greater than 4 to 6 mm: CT follow-up at 12 months (if unchanged, no further follow-up); nodule greater than 6 to 8 mm: CT at 6 to 12 months, then at 18 to 24 months if no change; nodule greater than 8 mm: CT at 3, 9, and 24 months or PET scan or biopsy.

For individuals in the high-risk category, the recommendations are as follows: nodule 4 mm or less: CT follow-up at 12 months (if unchanged, no further follow-up); nodule greater than 4 to 6 mm: CT follow-up at 6 to 12 months, then 18 to 24 months if no change; nodule greater than 6 to 8 mm: CT at 3 to 6 months, then at 9 to 12 and 24 months if no change; nodule greater than 8 mm: same as for low-risk patient.

The guidelines also point out that nonsolid (ground-glass) or partly solid nodules may require longer follow-up to exclude an indolent adenocarcinoma.

Case 104

1 Names at least four causes of tracheal narrowing.

2 Is post-intubation tracheal narrowing typically focal or diffuse?

3 What are some of the presenting symptoms of central airway obstruction?

4 What is the best imaging modality for detection of tracheal stenosis?

Answers

Case 104

Tracheal Stenosis

1 Post-intubation injury, malignant neoplasm, tuberculosis, Wegener’s granulomatosis, amyloidosis.

3 Cough, stridor, wheezing.

4 MDCT with multiplanar and three-dimensional renderings.

Reference

Lee KS, Yoon JH, Kim TK, et al: Evaluation of tracheobronchial disease with helical CT with multiplanar and three dimensional reconstruction: correlation with bronchoscopy. Radiographics 17:555-567, 1997.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, pp 290-299.

Comment

Tracheal stricture is the most common late complication of tracheal intubation and decannulation. In the illustrated case, the stenosis manifests as a characteristic focal, short-segment circumferential stenosis at the site of a previous tracheostomy. Tracheal stenosis, tracheomalacia, or an ulcerative tracheoesophageal fistula may develop at the stomal site, at the level of an endotracheal tube cuff, or at the site where the tip of a tracheal tube rests against the tracheal wall. Overdistention of an endotracheal tube cuff may produce pressure necrosis of the tracheal wall. Anterior angulation of an endotracheal tube may produce erosion of the tracheal wall and lead to perforation of the wall and even of the adjacent innominate artery; posterior angulation may result in a tracheoesophageal fistula.

On imaging studies, tracheal stenosis typically manifests as an hourglass-like stenosis. Tracheal stenosis may be missed on conventional chest radiography, and a negative radiograph does not exclude the diagnosis. MDCT is the imaging modality of choice and should include multiplanar and three-dimensional renderings when possible.

Case 105

1 Describe the normal configuration and location of the thymus gland on axial CT imaging.

2 Describe the range of CT attenuation values (Hounsfield units) of the normal thymus on CT imaging.

3 Name at least three causes of thymic hyperplasia.

4 Which imaging modality is most useful for distinguishing thymic hyperplasia from thymic neoplasia?

Answers

Case 105

Thymic Hyperplasia

1 Bilobed, “arrowhead” configuration in the prevascular region of the anterior mediastinum.

2 Soft tissue, soft tissue with fat (speckled), fatty replacement.

3 Myasthenia gravis, rebound thymic hyperplasia following chemotherapy or steroids, hyperthyroidism (Graves’ disease), rheumatoid arthritis, scleroderma, red cell aplasia.

4 MRI using a chemical shift technique.

Reference

Inaoka T, Takahashi K, Mineta M, et al: Thymic hyperplasia and thymus gland tumors: differentiation with chemical shift MR imaging. Radiology 243:869-876, 2007.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, pp 348-349.

Comment

The normal thymus decreases in size with age as it undergoes fatty infiltration; it is visualized in less than 50% of patients older than 40 years on CT and/or MRI studies. The normal thymus manifests in the prevascular region of the anterior mediastinum as a bilobed homogeneous structure of soft tissue attenuation on CT. With progressive involution and fatty infiltration, it may appear speckled and lobular in configuration.

Thymic enlargement may represent thymic hyperplasia or a thymic epithelial tumor. True thymic hyperplasia represents an increase in size and weight of the thymus with retention of its normal gross architecture and histologic appearance. This form of hyperplasia may occur as a rebound phenomenon following chemotherapy, steroid therapy, or recovery from a severe systemic stress or insult (“rebound thymic hyperplasia”). Lymphoid (follicular) hyperplasia refers to a distinct entity characterized by an increased number of lymphoid follicles that is not usually associated with thymic enlargement. It is most commonly associated with myasthenia gravis, but is also associated with autoimmune and systemic disorders, including hyperthyroidism (Graves’ disease), acromegaly, systemic lupus erythematosus, scleroderma, rheumatoid arthritis, and cirrhosis.

Chemical-shift MRI is a recently developed technique that may be helpful in distinguishing thymic hyperplasia from thymoma and other thymic epithelial tumors. In this technique, comparison between in-phase and out-of-phase gradient-echo images reveals homogeneously decreased signal intensity in normal thymus and thymic hyperplasia on out-of-phase images due to diffuse fatty infiltration, as shown in this case. In contrast, thymic epithelial neoplasms usually do not exhibit this pattern.

Case 106

1 Regarding solitary pulmonary nodules (SPNs), which is most likely to be malignant: a solid nodule, a ground-glass nodule, or a semi-solid nodule of mixed attenuation (ground-glass and solid components)?

2 What focal disease entities manifest most commonly on imaging studies as a solid nodule with a halo of surrounding ground-glass opacity?

3 In which clinical setting is invasive aspergillosis most likely to occur?

4 Bronchioloalveolar carcinoma (BAC) is a subtype of which lung cancer cell type?

Answers

Case 106

Mixed Attenuation SPN

1 A semi-solid nodule of mixed attenuation.

2 BAC, invasive aspergillosis, candidiasis, cytomegalovirus.

3 Severely neutropenic patient.

4 Adenocarcinoma.

Reference

Müller NL, Silva CIS: Nodules and masses. In: Silva CIS, Müller NL, Eds. Imaging of the Chest. Philadelphia: Saunders, 2008, pp 136-157.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, pp 284-286.

Comment

On thin-section CT, a malignant SPN may be of soft tissue or ground-glass attenuation, or a combination of both ground-glass and solid components (i.e., semi-solid or mixed attenuation). Of those patterns, the mixed attenuation (semi-solid) solitary nodule is the most likely to be malignant, and the soft tissue nodule is the most likely to be benign.

A mixed attenuation nodule with a halo of surrounding ground-glass opacity is also an imaging manifestations of invasive aspergillosis and candidiasis, typically occurring in a severely neutropenic patient, and of cytomegalovirus, most commonly occurring 1 month or longer following organ transplantation.

Besides the variability of their CT attenuation, malignant SPNs are also variable in their border characteristics and may manifest as spiculated, ill-defined, or well-defined nodular opacities.

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