Definition

Cardiac myxomas are benign neoplasms of endocardial origin, most commonly located in the atria.

Prevalence

With an incidence of 0.03%, cardiac myxoma is the most common primary cardiac tumor.¹ It represents approximately 50% of all benign cardiac tumors.² Myxomas have been reported in patients of every age, but most frequently patients present with myxomas between the third and sixth decades, with an average age of approximately 50 years.^2,3 There is a higher prevalence in women.²

A rare autosomal dominant form of cardiac myxoma is termed the Carney complex. Associated features include pigmented skin lesions, cutaneous myxomas, primary pigmented nodular adrenocortical disease, mammary myxoid fibroadenomas, large cell calcifying Sertoli-cell tumors, pituitary adenomas, thyroid tumors, and melanotic schwannomas.⁴ Patients with the Carney complex present at an earlier age compared with patients with sporadic cases of cardiac myxoma, with an average age of 26 years.⁴ These patients are also more predisposed to develop multiple tumors, documented in 41%⁴ compared with 6% of patients with sporadic cardiac myxomas.⁵

Pathology

Cardiac myxomas arise from the endothelial surface by either a narrow or a broad-based pedicle and extend into the cardiac chamber (intracavitary growth) (Fig. 67-1). They range in size from 1 to 15 cm in diameter (average 5 to 6 cm).² Approximately 75% originate in the left atrium, 15% to 20% originate in the right atrium, and 5% are biatrial.¹ Myxomas rarely occur within the ventricular chamber or along the atrioventricular valves. Most are smoothly marginated, firm, and fibrotic (Fig. 67-2). The remaining one third to one half are gelatinous and friable with a villous or frondlike surface (Fig. 67-3).¹ This latter type is the morphology typically found in the Carney complex and is more likely to produce embolization.⁶ Focal areas of hemorrhage may be evident on the surface of a myxoma.

FIGURE 67-1 Gross surface features of cardiac myxoma. Intraoperative photograph of a left atriotomy reveals a lobulated, hemorrhagic mass (asterisk) arising from the endothelial surface and extending into the left atrial chamber.

FIGURE 67-2 Gross surface features of cardiac myxoma. Gross specimen shows a glistening, smoothly contoured mass with focal areas of hemorrhage.

FIGURE 67-3 Gross surface features of cardiac myxoma. Gross specimen of a different myxoma shows an irregular, polypoid surface with multiple frondlike excrescences, predisposing to embolization.

Histologically, myxomas consist of inflammatory cells and myxoma cells in a myxoid matrix (Fig. 67-4). Myxoma cells are stellate multinucleate cells that form elongated cords and rings.⁶ They are of uncertain origin, but may arise from residual embryonal multipotential mesenchymal cells of the heart.² Myxomas also characteristically contain cysts, hemorrhage, extramedullary hematopoiesis and, rarely, glandular elements.⁶ Calcification is common microscopically, and for unknown reasons is more prevalent in lesions on the right side of the heart.¹

FIGURE 67-4 Intermediate-power photomicrograph shows nests of myxoma cells (arrows) embedded in a myxoid matrix (hematoxylin-eosin stain).

Manifestations of Disease

Imaging Techniques and Findings

Radiography

Findings on chest radiograph vary with tumor location. Approximately 50% of left atrial myxomas produce findings suggestive of mitral valve obstruction, such as left atrial enlargement, prominence of the left atrial appendage, vascular redistribution, and pulmonary edema (Fig. 67-5).³ Cardiomegaly and pleural effusions are less frequent findings, but may occur with either right-sided or left-sided myxomas. Radiographically evident calcification is reported in 50% of right atrial myxomas, but is not seen in left atrial myxomas.³ Approximately one third of chest radiographs are normal.³

FIGURE 67-5 Frontal chest radiograph in an elderly woman with progressive dyspnea shows vascular congestion, prominent septal (Kerley B) lines, small bilateral pleural effusions, and mild cardiomegaly with left atrial appendage enlargement. Presumptive diagnosis was congestive heart failure, but a left atrial myxoma was discovered by echocardiogram.

Ultrasonography

Transesophageal echocardiography may allow for better visualization of atrial tumors compared with the transthoracic approach (Fig. 67-6). Myxomas are pedunculated mobile masses on echocardiography, often apparently attached to the interatrial septum by a narrow stalk.⁷ Myxomas may be homogeneous or heterogeneous, with echogenic foci owing to calcification and hypoechoic areas from hemorrhage, necrosis, or cysts.⁷ Dynamic prolapse of the mass across the atrioventricular valve is often well visualized on echocardiography.

FIGURE 67-6 Two-dimensional transthoracic echocardiogram (four-chamber view) shows an echogenic mass (asterisk) filling the left atrium, confirmed intraoperatively as a left atrial myxoma.

Computed Tomography

On contrast-enhanced CT, cardiac myxomas appear as intracavitary round or ovoid filling defects with smooth or lobulated contours.³ Most myxomas are hypodense to myocardium and unopacified blood (Fig. 67-7).^3,5 Myxomas tend to enhance heterogeneously after administration of contrast medium (Fig. 67-8).³ CT may show a narrow base of attachment to the interatrial septum, although a pedicle is usually not as well seen as with echocardiography.⁷ Calcification may be evident, but typically only in right heart myxomas. Secondary complications of myxomas may be identified on CT, including pulmonary or visceral emboli and evolving infarction.³

FIGURE 67-7 Contrast-enhanced axial CT image (soft tissue windows) of a left atrial myxoma shows a lobulated, hypodense mass with a narrow base of attachment (arrow) to the interatrial septum.

FIGURE 67-8 Coned axial CT image (soft tissue windows; cardiac gated) of a heterogeneously enhancing right atrial myxoma (arrow).

Magnetic Resonance Imaging

On MRI, myxomas are usually isointense on T1-weighted sequences and high signal intensity on T2-weighted sequences because of their myxoid stroma composition (Fig. 67-9A and B).⁸ Myxomas are typically heterogeneous, likely reflective of varying components of hemorrhage, calcification, cysts, and myxoid or fibrous tissue.³ Loss of signal intensity occurs with gradient-recalled-echo (GRE) imaging possibly because of magnetic susceptibility from high iron content.³ Myxomas are usually hypointense to blood pool and hyperintense to myocardium on steady-state free precession (SSFP) sequences, although they may be isointense to blood and possibly missed on this sequence.⁹ Myxomas enhance with gadolinium, usually with a heterogeneous pattern on perfusion and delayed enhancement phases (Fig. 67-9C).¹⁰ MRI has been reported to be more accurate than CT in predicting the point of attachment to the wall, which may be best seen on cine images.³ Cine MRI also may show prolapse of the tumor across a cardiac valve (Fig. 67-10).¹⁰

FIGURE 67-9 Left atrial myxoma in a 17-year-old boy. A and B, On axial T1-weighted MR image (A), the lesion is isointense to slightly hyperintense in signal intensity, whereas axial T2-weighted MR image (B) shows marked homogeneous high signal intensity. C, Postgadolinium axial T1-weighted MR image shows heterogeneous enhancement. D, Intraoperative view of pedunculated left atrial myxoma.

(Courtesy of Gil Boswell, MD, Naval Medical Center San Diego.)

FIGURE 67-10 Horizontal long-axis cine images of a pedunculated left atrial myxoma in systole and diastole show partial prolapse of the lesion (asterisk) across the mitral valve plane during diastole.

Differential Diagnosis

The differential diagnosis of an intracavitary cardiac mass includes thrombus and other neoplasms, such as metastatic disease and sarcoma. As opposed to atrial myxomas, atrial thrombi are found in the setting of atrial fibrillation and mitral valve disease, and are usually located in the atrial appendage or posterior or lateral atrial walls, rather than along the interatrial septum. Additionally, thrombi do not typically show contrast enhancement, a feature best evaluated on MRI. Metastatic disease may occur in any location within the heart, but is most frequent in the right-sided chambers. Sarcomas are generally much more invasive and infiltrative in appearance.

Treatment Options

To prevent complications such as embolization or sudden cardiac death owing to valvular obstruction, the treatment of cardiac myxoma is prompt surgical resection. The stalk and zone of attachment are excised, including the full thickness of the interatrial septum for myxomas that arise in this location. Long-term prognosis is excellent. Recurrence occurs in less than 3% of nonfamilial cases and is considered related to incomplete resection.² In patients with the Carney complex, recurrence is 20%, which may be due in part to multifocality of lesions.^2,4

KEY POINTS: MYXOMA

Clinical and radiographic manifestations of cardiac myxomas may mimic valvular disease, particularly mitral stenosis.

Typical imaging appearance is an intracavitary, pedunculated mass located in the left atrium arising from the interatrial septum.

Contrast-enhanced MRI may help to distinguish between thrombus and myxoma.

Definition

Papillary fibroelastoma is an endocardial-based mass most commonly found on the aortic valve. It is of uncertain etiology and may be a hamartoma, neoplasm, or reparative process.

Prevalence

Cardiac papillary fibroelastomas are the second most common primary cardiac tumor, representing approximately 10% of benign cardiac tumors.⁷ They are the most common tumor of the cardiac valves. Papillary fibroelastomas have been reported in all ages, but are most frequently found in the fourth to eighth decades of life, with a mean age of 60 years.¹¹ In the largest case analysis, there was a slight male predominance of 55%.¹¹ This lesion is usually solitary, and no familial cases have been described.

Pathology

Papillary fibroelastomas consist of multiple fronds attached to the endocardium by a short pedicle. When immersed in water or saline, they are described as having the appearance of a sea anemone (Fig. 67-11).¹ The papillary fronds are avascular with an elastic fiber and collagen core surrounded by myxomatous matrix and endothelial cells.⁶ Dystrophic calcification has been reported, but is rare.¹¹ Most lesions are approximately 1 cm in maximum diameter, although lesions up to 7 cm in size have been reported.¹¹ More than 75% of papillary fibroelastomas are found on the cardiac valves, involving the aortic, mitral, tricuspid, and pulmonary valves in decreasing frequency.¹¹ Aortic and pulmonary valve papillary fibroelastomas most commonly project into the vascular lumen, whereas papillary fibroelastomas on the atrioventricular valves usually project into the atria.¹¹ They may also occur along the endocardial surfaces of the atria and ventricles or on the eustachian valve.

FIGURE 67-11 Immersed in fluid, a papillary fibroelastoma exhibits multiple branching papillary fronds, which create the appearance of a sea anemone.

Manifestations of Disease

Imaging Techniques and Findings

Radiography

Because of their small size, papillary fibroelastomas would not be expected to produce any findings on chest radiography. If there is obstruction of the mitral valve, findings of pulmonary venous hypertension may be apparent. Calcification is rarely visible.¹¹

Ultrasonography

Most papillary fibroelastomas are found incidentally during echocardiography. They typically appear as small, homogeneous, valvular masses that may be sessile or pedunculated.⁵ A stippled pattern may be seen near the edges, reflective of the papillary projections.¹¹ Almost half of papillary fibroelastomas are mobile with evidence of flutter or prolapse.^11,12

Computed Tomography

The few studies of the CT appearance of papillary fibroelastomas have used ECG gating. They describe a tiny, well-defined spherical mass attached to a valve leaflet (Fig. 67-12).^13,14

FIGURE 67-12 A 59-year-old woman with new cardiac murmur and 1-cm rounded lesion identified on the aortic valve by echocardiogram. A, Contrast-enhanced, cardiac gated CT image (soft tissue windows), reconstructed through the aortic valve plane, shows a 9-mm lesion (arrow) attached to the right aortic valve cusp. B, Intraoperative photograph reveals a papillary-appearing lesion at the leading edge of the mid–right coronary cusp of the aortic valve.

Magnetic Resonance Imaging

Because of their small size, papillary fibroelastomas are infrequently visualized on MRI. Papillary fibroelastoma is typically a mobile, nodular mass with homogeneous intermediate signal intensity on T1-weighted sequences and intermediate or low signal intensity on T2-weighted sequences.^14,15 It is best appreciated on cine MRI sequences as a small valvular mass with adjacent turbulent blood flow.¹⁰ It is characteristically hypointense to myocardium on GRE sequences.¹⁶ After administration of gadolinium, papillary fibroelastomas show delayed hyperenhancement possibly because of their fibroelastic tissue composition.^13,17

Differential Diagnosis

The differential diagnosis of a cardiac valvular mass includes vegetation from endocarditis, thrombus, and valvular myxoma. The clinical context of endocarditis differs from papillary fibroelastoma. Additionally, these entities can be differentiated on imaging by the function of the underlying valve. Leaflet destruction and valvular incompetence are usually seen in endocarditis, but normal valve function is preserved in the presence of a papillary fibroelastoma. Valvular thrombus usually is nonmobile and lacks enhancement. Valvular myxomas are usually larger than papillary fibroelastomas and may be differentiated by their heterogeneous and high T2 signal intensity on MRI.

Treatment Options

Treatment is surgical excision, particularly for left-sided lesions, to prevent the consequences of systemic embolization. Recurrence has not been reported.¹¹ The efficacy of long-term anticoagulation is unknown.

KEY POINTS: PAPILLARY FIBROELASTOMA

Papillary fibroelastoma is the most common cardiac valve tumor.

It is most frequently located on the aortic or mitral valves, and is a potential source of systemic emboli.

Definition

Cardiac fibroma is a congenital neoplasm or hamartoma of fibrous tissue that usually manifests in childhood.

Prevalence

Cardiac fibromas are the second most common tumor in childhood after rhabdomyoma. In contrast to rhabdomyomas, they are uniformly solitary.⁵ One third of patients present before 1 year of age, although 15% of cardiac fibromas are discovered in adolescence and adulthood.⁵ There is no sex predilection.¹⁸ Fibromas are associated with Gorlin syndrome (also known as basal cell nevus syndrome), an autosomal dominant syndrome of multiple basal cell carcinomas, odontogenic keratocysts, skeletal anomalies, and other neoplasms such as medulloblastoma.⁸

Pathology

Fibromas are mural-based whorled masses of white tissue (Fig. 67-13). Mean size is 5 cm (range 2 to 10 cm).^5,7 They are not encapsulated and may have either circumscribed or infiltrating margins. Fibromas are typically located in the interventricular septum or left ventricular free wall.^1,6 Less frequently, they are found in the right ventricle or atria. In newborns and infants, fibromas are highly cellular with numerous fibroblasts. With age, cellularity decreases, and the amount of collagen increases.^6,19 Fibromas contain microscopic calcification in one third of cases; they are otherwise fairly homogeneous on histologic and gross examination.⁶

FIGURE 67-13 Gross photo of a ventricular fibroma (cut section) reveals firm, whorled white tissue.

Manifestations of Disease

Imaging Techniques and Findings

Radiography

The most common abnormality on chest radiograph is cardiomegaly.²² A focal bulge of the cardiac contour can also be seen.¹⁹ Calcification overlying the cardiac silhouette is visualized radiographically in approximately one quarter of cases, and may appear dense or amorphous.^5,20

Ultrasonography

Cardiac fibroma may appear as a discrete mass or a focal area of wall thickening mimicking focal hypertrophic cardiomyopathy on echocardiogram. Fibromas are echogenic and may appear heterogeneous.⁵

Computed Tomography

Fibromas are circumscribed or infiltrative mural-based masses on CT (Fig. 67-14A). They show soft tissue attenuation and often calcification.⁸ Enhancement may be either homogeneous or heterogeneous.^5,19

FIGURE 67-14 An asymptomatic 45-year-old man with left ventricular fibroma. A, Axial CT angiogram shows an oblong, homogeneous soft tissue mass (arrows) in the lateral left ventricle, partly surrounded by epicardial fat. B, Axial MR image (double inversion recovery) at similar level to the CT angiogram confirms an oblong, hypointense mass (arrows) associated with the left ventricular wall, partly outlined by epicardial fat. C, Short-axis MRI perfusion (left) and delayed enhancement (right) images. Perfusion image shows the lesion (arrow) relatively hypointense compared with adjacent myocardium; delayed phase imaging reveals characteristic intense hyperenhancement of the lesion (arrow).

Magnetic Resonance Imaging

On MRI, a cardiac fibroma appears as an intramural mass or focal myocardial thickening on T1-weighted sequences, where it is isointense or hypointense to myocardium (Fig. 67-14B).^8,23 In contrast to other cardiac tumors, fibromas are characteristically hypointense on T2-weighted and SSFP sequences because of their fibrous tissue composition, which has low water content.^8,23,24 The fibrous tissue is also hypovascular, causing little or no enhancement on perfusion imaging (Fig. 67-14C).²⁴ On myocardial delayed enhancement MRI, fibromas typically show marked hyperenhancement, however, occasionally with central regions of hypointensity (see Fig. 67-14C).²⁴ The delayed enhancement is currently attributed to the significant extracellular space for gadolinium accumulation.²⁴

Differential Diagnosis

The differential diagnosis of a cardiac mass in an infant or child is rhabdomyoma, fibroma, and rhabdomyosarcoma. Rhabdomyoma is supported by findings of tuberous sclerosis, multiplicity, and lack of calcification. Rhabdomyosarcoma may be discriminated by its heterogeneous appearance, reflecting cystic change and necrosis.

Treatment Options

In contrast to soft tissue fibromatosis, there is little evidence that cardiac fibromas may enlarge, and spontaneous regression has been reported.¹ Treatment for symptomatic patients is complete surgical excision, although partial excision may be performed for more extensive tumors. Postsurgical recurrence is rare.⁵

KEY POINTS: FIBROMA

Fibroma should be considered in the differential diagnosis of a solitary mural-based mass in a child.

Characteristic MRI appearances are hypointensity on T2-weighted sequences, minimal enhancement on perfusion images, and marked hyperenhancement on myocardial delayed enhancement imaging.

Definition

Rhabdomyoma is a congenital hamartoma of altered cardiac myocytes.

Prevalence

Rhabdomyoma is the most common cardiac neoplasm in infants and children, and accounts for 50% to 75% of pediatric cardiac tumors.¹⁰ It occurs equally in boys and girls.¹⁰ Approximately 50% of patients with rhabdomyomas have tuberous sclerosis, an association that increases to 95% in fetuses and neonates with multiple cardiac tumors.²⁵ Conversely, virtually all infants with tuberous sclerosis have cardiac rhabdomyomas, although this incidence decreases with age because of spontaneous regression.⁸ Rhabdomyoma is rarely associated with congenital heart diseases, such as Ebstein anomaly, tetralogy of Fallot, and hypoplastic left heart syndrome.²²

Pathology

Rhabdomyomas usually consist of circumscribed mural-based nodules that average 1 to 3 cm in size; multiple nodules are present in 70% to 90% of cases.¹ The left ventricle or interventricular septum is the most common location, followed by the right ventricle and atria in decreasing frequency.²⁶ Rhabdomyomas protrude into the cardiac chambers in 50%,²⁷ a characteristic observed more often in patients who do not have tuberous sclerosis.⁶ Histologically, the rhabdomyoma cell has a distinctive spider-like appearance with vacuolated cytoplasm and radiating myofibers surrounding a central nucleus. The cells stain with periodic acid–Schiff because of their high glycogen content.⁵

Manifestations of Disease

Imaging Techniques and Findings

Radiography

Chest radiographs may show cardiomegaly.²²

Ultrasonography

Prenatal and postnatal echocardiograms show intramural, solid hyperechoic masses typically located in the ventricular myocardium.

Computed Tomography

CT scan may show multiple intramural nodules that appear either hypodense or hyperdense to normal myocardium.²⁸

Magnetic Resonance Imaging

Cardiac rhabdomyomas are intramural masses that are isointense on T1-weighted MRI sequences and hyperintense on T2-weighted sequences (Fig. 67-15).⁸ They may produce focal abnormalities of contractility.⁸ Rhabdomyomas enhance homogeneously and intensely with gadolinium.^8,10 Numerous rhabdomyomas less than 1 mm in size, so-called rhabdomyomatosis, may produce diffuse myocardial thickening without a discrete mass.⁵³

FIGURE 67-15 Obstetric ultrasound examination in a 33-week gestational age fetus showed a large “mediastinal mass.” A, MR image (SSFP) oriented in the coronal plane of the fetus shows a large mass (asterisk) inseparable from the heart, with mass effect on the remainder of the heart and both lungs. Note small pleural effusions, ascites, subcutaneous edema, and polyhydramnios. B, Autopsy reveals a large, 7 × 5 × 5 cm left ventricular rhabdomyoma (asterisk) that fills the chest cavity and, by mass effect, rotates the heart in an abnormal orientation and causes pulmonary hypoplasia. Note residual pacemaker wires.

Differential Diagnosis

The differential diagnosis of a neonatal cardiac mass includes rhabdomyoma, fibroma, teratoma, and rhabdomyosarcoma. Rhabdomyomas are typically multifocal and lack the calcification and T2 hypointensity of fibromas, or the heterogeneity of teratomas and rhabdomyosarcomas.

Treatment Options

Approximately 80% of cardiac rhabdomyomas regress spontaneously during childhood and are not resected, unless life-threatening symptoms are present.²⁷ They regress less frequently, however, in patients who do not have tuberous sclerosis, more often requiring surgical excision.⁸

KEY POINTS: RHABDOMYOMA

Rhabdomyoma is the most common cardiac tumor of childhood.

Half of patients with rhabdomyoma have tuberous sclerosis, and virtually all patients with tuberous sclerosis have cardiac rhabdomyomas.

The typical imaging appearance is multiple ventricular mural-based masses.

Definition

Lipomas are true neoplastic lesions of mature fat cells.

Prevalence

Lipomas reportedly represent 8% of primary cardiac tumors,²⁹ although this may be an overestimate because many series do not differentiate lipomas from LHIS. They may manifest at any age, but patients are typically younger than patients with lipomatous hypertrophy.³⁰ There is no gender prevalence.²⁹

Pathology

Lipomas are circumscribed masses of homogeneous yellow fat that may be found within the myocardium, occasionally with extension into the pericardial space or cardiac chambers. The most common sites are the right atrium, left ventricle, and interatrial septum.²⁹ Half are subendocardial, with the remaining half split between myocardial and subepicardial locations.²⁹ Histologically, lipomas are encapsulated masses of mature fat cells, without the brown fat or hypertrophic myocytes found in lipomatous hypertrophy.

Manifestations of Disease

Imaging Techniques and Findings

Radiography

Chest radiographs may be normal or show cardiomegaly.⁵

Ultrasonography

Lipomas are nonspecific homogeneous, immobile echogenic masses on echocardiography.⁵

Computed Tomography

CT and MRI have the advantage over echocardiography of being able to characterize the tissue type. Lipomas have homogeneous low attenuation on CT similar to subcutaneous or mediastinal fat, typically less than −50 Hounsfield units (Fig. 67-16). Thin strands of soft tissue attenuation septa may be present without any nodularity. No significant enhancement occurs with administration of contrast medium.

FIGURE 67-16 A 26-year-old woman with palpitations. A and B, Axial CT slice (A) and two-chamber view reformat (B) (soft tissue windows) show a rounded filling defect of fat density at the left ventricular apex (arrows). C, Gross photograph of the left ventricular lipoma with fragments of cardiac muscle (asterisk); at surgery, the 2.4 × 1.3 cm lesion was attached to the anterolateral papillary muscle.

Magnetic Resonance Imaging

On MRI, lipomas are homogeneous, smoothly contoured masses. They show homogeneous fat signal intensity on all sequences, including decreased signal intensity on fat-suppressed sequences, and no enhancement with gadolinium.^8,29 There may be thin septations, but no nodular components. Chemical shift artifact occurs on SSFP sequences at the interface between the lipoma and the myocardium or blood pool, resulting in a low signal intensity margin.²⁹

Differential Diagnosis

In the differential diagnosis of a fat-containing cardiac mass, LHIS should be considered for lesions located in the interatrial septum. A true lipoma is more often round or oval instead of bilobed, discovered incidentally in younger patients or in patients with little mediastinal fat. Liposarcoma is also in the differential diagnosis of a fat-containing cardiac mass, although it usually contains significant soft tissue components.

Treatment Options

Surgical resection is performed only for symptomatic cardiac lipomas.

KEY POINTS: LIPOMA

CT and MRI are diagnostic for lipomas, showing homogeneous fat-containing masses without soft tissue components other than thin septations.

Lipomas tend to be found in a younger patient population than LHIS.

Definition

LHIS is not a true neoplasm, but rather a benign diffuse thickening (defined as >2 cm) of the normal extension of epicardial fat within the interatrial groove.³⁰

Prevalence

LHIS is significantly more common than true cardiac lipomas. In a prospective study of sequential chest CT scans, the incidence was 2.2%.³¹ The reported age range is 22 to 91 years, with most patients presenting with LHIS older than 60 years.³⁰ Associations include age, obesity, pulmonary emphysema, and long-term parenteral nutrition.³¹ Some reports suggest a slight female predominance.^30,31

Pathology

Lipomatous hypertrophy is a misnomer because the lesion actually represents hyperplasia rather than hypertrophy of the normal fat found within the interatrial septum. LHIS is a nonencapsulated, poorly circumscribed thickening of the fat of the interatrial groove that extends from the aortic root caudally to the coronary sinus; it is occasionally contiguous with mediastinal fat. LHIS spares the fossa ovalis, causing a bilobed appearance. In a prospective CT study, the thickness ranged from 2 to 6.2 cm (mean 3.2 cm).³¹ A combination of vacuolated brown fat cells, hypertrophic myocytes, and normal mature fat cells is seen on histologic examination.⁶

Manifestations of Disease

Imaging Techniques and Findings

Ultrasonography

Echocardiography shows an echogenic, dumbbell-shaped mass in the interatrial septum sparing the fossa ovalis.³²

Computed Tomography

CT reveals a homogeneous fatty attenuation mass, shaped like an hourglass or a dumbbell, which shows focal sparing at the fossa ovalis (Fig. 67-17). No significant enhancement occurs with administration of contrast medium. A large amount of concomitant epicardial or mediastinal fat, or both, is often present.^29,31

FIGURE 67-17 A 74-year-old woman with LHIS, an incidental finding. Contrast-enhanced coned axial CT image (soft tissue windows) shows a dumbbell-shaped, homogeneous lesion of fat density (arrows) located in the interatrial septum, with sparing of the fossa ovalis (arrowhead). Note prominence of epicardial and mediastinal fat planes.

Magnetic Resonance Imaging

LHIS also has an hourglass shape on MRI. It is homogeneous and similar in signal intensity to subcutaneous or mediastinal fat on all sequences, with signal dropout on fat saturation sequences (Fig. 67-18A).²⁹ SSFP sequences show central hyperintensity with a low signal intensity margin at the interface with blood or myocardium, presumably from chemical shift artifact (Fig. 67-18B).²⁹

FIGURE 67-18 An 80-year-old woman with an incidental finding. A, Horizontal long-axis T1-weighted MR image (without and with fat saturation). Without fat saturation, the bilobed mass (arrow) has high signal intensity that matches the subcutaneous fat. With fat saturation, the mass (arrowhead) shows decreased signal intensity, which confirms its fatty composition. B, Horizontal long-axis cine image shows characteristic low signal intensity margin (arrowheads) outlining the lipomatous hypertrophy.

Nuclear Medicine

In positron emission tomography (PET) imaging with ¹⁸FDG, increased uptake of ¹⁸FDG compared with background mediastinum has been reported and is presumably related to the presence of brown fat.³³

Differential Diagnosis

The differential diagnosis of LHIS includes other fat-containing masses, such as lipoma and liposarcoma. Cardiac lipomas typically do not have a bilobed appearance and can be found in any location within the heart. Cardiac liposarcoma is extremely rare, and nonlipomatous soft tissue components may be expected on imaging.

Treatment Options

Surgical resection may be performed in cases causing arrhythmias unresponsive to medical treatment, or in cases with LHIS lesions causing obstruction of the superior vena cava or right atrium.

KEY POINTS: LIPOMATOUS HYPERTROPHY OF THE INTERATRIAL SEPTUM

Although usually incidental, LHIS is a cause of supraventricular arrhythmias.

Imaging appearance is diagnostic, with an hourglass-shaped mass of fat attenuation or fat signal intensity in the interatrial septum.

Definition

A cardiac paraganglioma is an extra-adrenal catecholamine-producing tumor derived from chromograffin neuroectodermal cells.

Prevalence

Cardiac paragangliomas are extremely rare. Only 1% to 2% of pheochromocytomas or paragangliomas are found within the thorax, most of which are located in the posterior mediastinum. Cardiac paragangliomas typically manifest in adulthood, with an age range of 18 to 85 years (mean 40 years).⁵ Extracardiac paragangliomas occur in about 5% to 10% of patients with a cardiac paraganglioma.³⁴ Metastatic disease also occurs in 5% to 10% of cases of cardiac paragangliomas, typically involving the skeleton. Cardiac paraganglioma has been described in a patient with the Carney triad, which consists of gastrointestinal stromal tumor, pulmonary chondroma, and extra-adrenal pheochromocytoma.³⁴ To our knowledge, cardiac paragangliomas have not been reported in patients with multiple endocrine neoplasia syndromes.

Pathology

Cardiac paragangliomas are usually masses 3 to 8 cm in diameter with encapsulated or infiltrative margins and central necrosis.⁸ They follow the distribution of cardiac paraganglia, most involving the left atrium.^34,35 Other reported locations include the interatrial septum, the anterior surface of the heart, the right atrium, the aortic root, and the left ventricle.³⁵ Cardiac paragangliomas have identical histology to extracardiac paragangliomas, with nests of paraganglial cells, described as zellballen, surrounded by sustentacular cells (Fig. 67-19).^5,6

FIGURE 67-19 High-power photomicrograph of a paraganglioma shows the typical nesting (zellballen) appearance of paraganglial cells (hematoxylin-eosin stain).

Manifestations of Disease

Imaging Techniques and Findings

Radiography

In a small series, the most common finding on chest radiographs was a middle mediastinal mass, most splaying the carina.³⁴

Ultrasonography

Cardiac paragangliomas are echogenic masses most often involving the left atrium.⁷ Echocardiography may show compression of nearby structures, including the superior vena cava.

Computed Tomography

CT reveals a mass typically involving the roof or posterior wall of the left atrium with circumscribed or infiltrative margins.³⁴ Enhancement is usually intense, with about half of cases showing peripheral enhancement with central low attenuation areas compatible with cystic change or necrosis.⁵

Magnetic Resonance Imaging

Cardiac paragangliomas are isointense or hypointense to myocardium on T1-weighted MRI sequences (Fig. 67-20A), although they may contain areas of hyperintensity from hemorrhage. On T2-weighted sequences, they are generally markedly hyperintense and may appear “light-bulb bright” (Fig. 67-20B), similar to their adrenal counterpart.⁸ Paragangliomas often show intense, heterogeneous enhancement with central nonenhancing components attributable to foci of necrosis (Fig. 67-20C).⁸

FIGURE 67-20 A 38-year-old man with generalized weakness and left upper extremity paresthesias. A, T1-weighted axial MR image shows a multilobulated mass (asterisk) centered in the left atrium with extension into the right atrium. At surgery, a 5 × 3 × 4 cm paraganglioma was identified straddling the foramen ovale. B, T2-weighted fat-saturated axial MR image shows a slightly heterogeneous mass (asterisk) filling the left atrium, which is hyperintense compared with the myocardium. C, First-pass perfusion MR image shows rapid enhancement of the mass (arrows) compatible with the highly vascular nature of a paraganglioma. D, Gross image of resected atrium shows the fleshy pink rounded tumor (asterisk).

Nuclear Medicine

Nuclear medicine imaging with iodine 131 or iodine 123 MIBG is often used to localize extra-adrenal paragangliomas. These studies show focal abnormal uptake in almost all cases of cardiac paraganglioma and may show metastatic or multifocal disease.³⁴

Differential Diagnosis

The differential diagnosis of a left atrial mass includes myxoma and sarcoma. Clinical and laboratory abnormalities occurring with paragangliomas secondary to catecholamine excess are the most diagnostic findings. On CT and MRI, heterogeneity and a broad base of attachment favor paraganglioma over myxoma. Imaging findings cannot differentiate paraganglioma from primary cardiac sarcomas.

Treatment Options

Surgical resection with reconstruction is the treatment of choice when feasible. If the lesion is not resectable, heart transplantation and medical management with α and β blockade are options in symptomatic patients.

KEY POINTS: PARAGANGLIOMA

Paragangliomas are prominently enhancing masses in the left atrial posterior wall or roof.

Laboratory abnormalities of elevated catecholamines are diagnostic.

Definition

Calcified amorphous tumor is a rare, non-neoplastic, diffusely calcified mass of uncertain etiology.

Prevalence

Prevalence of calcified amorphous tumor is extremely low, with very few case reports in the literature. In the largest series of 11 cases, the age range at presentation was 16 to 75 years (mean 52 years).³⁷

Pathology

Most cases of calcified amorphous tumor are pedunculated intracavitary masses, although it has also been reported to involve diffusely the myocardium, papillary muscles, and valve chordae.^37,38 The tissue is grossly a yellow-white color (Fig. 67-21). Microscopic analysis shows nodular deposits of calcium within a background of amorphous fibrinous material.³⁷ One hypothesis for the origin of calcified amorphous tumor is degeneration and organization of intramural thrombus; however, hemosiderin and laminations, usually found in organizing thrombi, are rare within this lesion.³⁷

FIGURE 67-21 Calcified amorphous tumor. A and B, Intraoperative view of opened right atrium (A) and specimen photograph (B) reveal a glistening white, granular-appearing lesion containing pink tissue.

Manifestations of Disease

Imaging Techniques and Findings

Radiography

Chest radiograph may show dense calcification within the cardiac silhouette (Fig. 67-22A).³⁸

FIGURE 67-22 A 51-year-old asymptomatic woman with calcified amorphous tumor of the right atrium and remote history of breast cancer. A, Posteroanterior and lateral chest radiographs (narrow window) coned to the cardiac silhouette show a calcified masslike opacity (arrows) located in the right atrium. B, MR cine image (four-chamber view) shows a broad-based intracavity right atrial mass (asterisk) marginated by multiple, small frondlike projections. C, Gadolinium-enhanced T1-weighted axial MR image shows a mass of predominantly low signal intensity (arrow) containing a few punctate areas of mild enhancement.

Ultrasonography

Most lesions evaluated with echocardiography were pedunculated, intracavitary diffusely calcified masses.³⁷

Computed Tomography

There is little literature regarding cross-sectional imaging of calcified amorphous tumor of the heart. Two studies that include CT findings describe a pedunculated, calcified right ventricular mass in one case,³⁹ and diffuse dense calcification of the left ventricle apical, septal, and lateral walls; papillary muscles; and mitral chordal apparatus in the other.³⁸

Magnetic Resonance Imaging

A single case report of a calcified amorphous tumor that includes MRI evaluation describes a right ventricular immobile broad-based mass.⁴⁰ Signal intensity is low on T1-weighted, T2-weighted, and delayed enhancement MRI sequences (Fig. 67-22B and C).⁴⁰

Differential Diagnosis

The differential diagnosis of a calcified cardiac mass includes neoplasms such as cardiac myxoma, fibroma, and osteosarcoma, and non-neoplastic causes of calcification, such as calcified thrombus, tumoral calcinosis, and prominent mitral annular calcification. Imaging findings are not specific.

Treatment Options

Treatment is surgical excision or heart transplantation if the infiltration is extensive. Postoperative recurrence has been reported.³⁸

KEY POINTS: CALCIFIED AMORPHOUS TUMOR OF THE HEART

Calcified amorphous tumor is an extremely rare cause of a diffusely calcified cardiac mass.

Definition

Cardiac metastases are malignancies that involve the myocardium, endocardium, epicardium, or pericardium secondarily. The pathways of spread include direct extension from a mediastinal or thoracic tumor, hematogenous spread, lymphatic spread, and intracavitary extension via the inferior vena cava or pulmonary veins (Figs. 67-23 through 67-26). Lung carcinoma, breast carcinoma, mesothelioma, and other thoracic malignancies may directly invade the heart and pericardium by contiguous growth. Melanoma, sarcomas, leukemia, and renal cell carcinoma tend to deposit neoplastic cells hematogenously within the myocardium. Epithelial malignancies, such as lung or breast carcinoma, tend to metastasize to the heart via lymphatic channels; regional lymphadenopathy and pericardial involvement often accompany superficial myocardial infiltration in these cases. Endovascular spread to the right heart via systemic venous drainage is characteristic of melanoma and renal, adrenal, hepatic, and uterine tumors. Lung neoplasms may invade the left atrium via a pulmonary vein. Lymphomas and leukemias secondarily involve the heart via any of the above-described pathways, typically affecting pericardium, epicardium, and myocardium diffusely.¹

FIGURE 67-23 Contiguous tumor spread to the heart. Contrast-enhanced coned axial CT image (soft tissue windows) reveals an aggressive left lower lobe lung cancer (asterisk) directly invading pericardium and myocardium, with nodular intracavitary extension into the left ventricular chamber (arrow).

FIGURE 67-24 Hematogeneous tumor spread to the heart. Gross section through the ventricles from a patient with metastatic melanoma reveals multiple intramural nodules (arrows), many showing hemorrhagic features, compatible with hematogenous metastases to the left ventricular myocardium.

FIGURE 67-25 Endovascular tumor spread to the heart. Coronal MR image (SSFP) of a leiomyosarcoma (asterisk) extending superiorly via the inferior vena cava to fill the right atrial chamber (arrow).

FIGURE 67-26 Contiguous spread to the heart via the pulmonary vein. Contrast-enhanced coned axial CT image (soft tissue windows) shows a right lower lobe lung cancer (asterisk) invading the left atrium via the right inferior pulmonary vein (arrow).

Pathology

On gross inspection, metastatic deposits in the heart vary in appearance and may be multinodular, diffusely infiltrative, or, less likely, a single mass. Tumor deposits may be evident on the pericardial surface. Mediastinal nodal enlargement is reported in 80% of cases. On histologic examination, metastatic foci in the heart tend to show features that identify the primary extracardiac malignancy. Sarcomatous deposits from an extracardiac tumor may be difficult to discern, however, from a primary cardiac sarcoma with intracardiac spread of disease. Extracardiac sarcomas that metastasize to the heart include osteosarcoma, liposarcoma, leiomyosarcoma, rhabdomyosarcoma, neurofibrosarcoma, synovial sarcoma, and MFH. In some instances, immunohistochemical markers may help to make the distinction between an extracardiac sarcoma and a primary cardiac sarcoma.¹

Manifestations of Disease

Imaging Techniques and Findings

Radiography

The chest radiograph is often unremarkable in cardiac metastatic disease. It may show global enlargement of the cardiac silhouette, however, if a large pericardial effusion is present (Fig. 67-27A). Pulmonary or mediastinal neoplasm, lymphadenopathy, or underlying metastatic disease in the lungs may be evident radiographically in some cases.

FIGURE 67-27 A 17-year-old girl with dysrhythmias and history of resected nevus containing melanoma 2 years earlier. A, Portable chest radiograph shows congestive heart failure with enlarged cardiomediastinal silhouette, diffuse ground-glass opacities, and prominent vasculature. B, Contrast-enhanced coned axial CT image (soft tissue windows) shows slightly hypodense lobulated masses centered in the interventricular septum (arrow) and left ventricle (arrowhead). C, T1-weighted axial MR image reveals multifocal, hyperintense masses (arrows) within the interventricular septum and the left and right ventricular walls. High T1 signal is compatible with metastatic melanoma. D, Gross autopsy specimen photograph (coned to the left ventricle) reveals a bulky, infiltrative mass (asterisk) located within the wall of the left ventricle and interventricular septum, which was histologically confirmed as melanoma. There are additional widespread tumor nodules studding the pericardium (arrows) and endocardium (arrowheads).

Ultrasonography

Transthoracic echocardiography in cardiac metastatic disease may show pericardial effusion or intracavitary, nonmobile and nonpedunculated masses, or both. Cardiac geometry and function may be assessed with parameters of possible obstruction, chamber dilation, compromised valve movement, hypokinesis, and elevated pressure gradients at ventricular outflow tracts.^45,46

Computed Tomography

CT provides a more detailed picture of intrathoracic anatomy, potentially revealing a lung carcinoma, pleural-based tumor (e.g., mesothelioma), or mediastinal mass (e.g., lymphoma) with contiguous cardiac invasion. CT may also identify a primary neoplasm or underlying metastatic disease, or both, elsewhere in the chest or upper abdomen. Intramural metastatic tumor deposits in the heart may be evident as myocardial-based nodules or masses (Fig. 67-27B). CT may show aggressive features, including multichamber involvement, intracavitary or intravascular tumor extension, engulfment of the cardiac valves, and pericardial infiltration (Fig. 67-28).^42,47 A moderate or large pericardial effusion may be evident and, in advanced cases, accompanied by pericardial thickening or nodularity (Fig. 67-29).

FIGURE 67-28 A 42-year-old woman with progressive dyspnea and history of metastatic cervical carcinoma. Cardiac gated, contrast-enhanced axial CT image (soft tissue windows) shows an aggressive-appearing infiltrative, multilobulated soft tissue mass (asterisk) involving right atrial and ventricular chambers with involvement of the tricuspid valve and contiguous spread to the pericardium (arrow).

FIGURE 67-29 A 53-year-old man with metastatic lung carcinoma. Contrast-enhanced coned axial CT image (soft tissue windows) reveals a left lower lobe mass (asterisk), intramural nodules in the right atrial wall (arrow), and nodular thickening and irregular enhancement (arrowheads) of the pericardium. Note also bowing of the interventricular septum and encasement of the ventricles, which support the diagnosis of cardiac tamponade.

(Courtesy of Tan-Lucien Mohammed, MD, Cleveland Clinic.)

Magnetic Resonance Imaging

MRI allows for the differentiation between tumor, cardiac anatomy (myocardium), thrombus, and blood flow artifact. Most cardiac neoplasms are of low signal intensity on T1-weighted images and are brighter on T2-weighted images; they also tend to enhance after intravenous contrast medium administration.⁴² In the case of metastatic melanoma, intramural nodular deposits characteristically appear bright on T1-weighted and T2-weighted MR images because of the presence of paramagnetic metals bound by melanin (see Fig. 67-27C and D).⁴² Cine MRI may be helpful to confirm the presence of intravascular or valvular tumor extension (Fig. 67-30). Gadolinium-enhanced MR images may help to distinguish intracavitary tumor from thrombus; enhancement and neovascularity are characteristic of most neoplasms, but not typical of thrombus.⁴² Changes in cardiac function, including compromised cardiac wall motion and myocardial viability, may also be viewed on MRI.⁴⁸ It may be difficult to discern benign from malignant cardiac masses based on either CT or MRI; it may not be obvious that the lesion is a metastatic versus a primary cardiac neoplasm unless other evidence exists to suggest the diagnosis.

FIGURE 67-30 A 57-year-old woman with cough, progressive dyspnea, and metastatic cervical carcinoma. A, Axial SSFP MR image shows a mass filling the right ventricular chamber (asterisk) with nodular extension through the tricuspid valve (arrow) into the right atrium. B, Sagittal SSFP MR image shows the right ventricular mass (asterisk) extending across the pulmonary valve (arrows).

Differential Diagnosis

Significant pericardial effusion in a patient with underlying malignancy may represent not only advanced neoplastic disease, but also concomitant infectious, drug-induced, radiation-induced, or idiopathic pericarditis.⁴² An intracardiac mass with multiple myocardial components may represent metastasis, but the differential diagnosis includes unusual primary cardiac neoplasms such as leiomyosarcoma, rhabdomyosarcoma (in children and young adults), rhabdomyoma (in infants), and PCL (in immunosuppressed patients).

Treatment Options

Metastatic tumors in the heart are surgically resected for palliation rather than cure. The clinical goal is at least temporary improvement of cardiac function. Long-term prognosis is poor.¹

KEY POINTS: METASTASES

Metastases to the heart are far more common than primary cardiac malignancies.

Malignancies most likely to involve the heart secondarily are lung and breast carcinomas, lymphomas, melanoma, and leukemias.

Malignant pericardial effusion is often the first clinical expression of cardiac metastatic disease.

Right atrial masses may reflect contiguous endovascular invasion by hepatic, renal, adrenal, or uterine malignancy.

Definition

Cardiac sarcomas arise from pleuropotential mesenchymal cells within the cardiac muscle.¹ In contrast to most other histologic subtypes of cardiac sarcomas (which typically arise in the left atrium), angiosarcomas are located in the right atrium in greater than 90% of cases. Angiosarcomas often infiltrate the pericardium, leading to malignant pericardial effusion.

Prevalence

Primary cardiac sarcomas as a group are rare (<25% of primary cardiac tumors). Angiosarcomas are the most common differentiated histologic subtype (37% of cardiac sarcomas), but the unclassifiable cardiac sarcomas seem to occur with equal frequency.^1,49 Mean age at presentation is approximately 40 years (range 3 months to 80 years) with a male predilection (2.5 : 1).²¹

Pathology

On gross inspection, angiosarcomas are multinodular, hemorrhagic masses centered in the right atrial wall, often with sheetlike pericardial invasion and thickening (Fig. 67-31). There may be contiguous involvement of the venae cavae and tricuspid valve. Histologic features include anastomosing vascular channels lined by malignant endothelial cells that may occasionally form atypical papillary tufts. Vacuoles containing red blood cells may be seen, and most lesions contain areas of necrosis.^1,21 Findings of high mitotic rate and necrosis are important predictors of poor patient survival.¹

FIGURE 67-31 Gross specimen photograph of a cardiac angiosarcoma reveals an infiltrative mass with multiple vacuoles containing hemorrhagic material (arrows).

Manifestations of Disease

Imaging Techniques and Findings

Radiography

At diagnosis, approximately 30% of patients with cardiac angiosarcoma have pulmonary nodules on the initial chest radiograph compatible with metastases.¹ Enlargement of the cardiac silhouette may reflect an underlying malignant pericardial effusion.

Ultrasonography

Echocardiography may reveal a broad-based, chiefly intramural right atrial mass located near the inferior vena cava. Pericardial effusion or contiguous tumor extension into the pericardium, endocardium, and left atrial chamber may be identified.²⁷

Computed Tomography

CT often shows a fairly well-defined, enhancing right atrial mass. In many cases, associated pericardial thickening, nodularity, and effusion are present (Fig. 67-32).⁴⁹ Pulmonary metastases may be evident, occasionally framed by halos of ground glass because of their hemorrhagic character (Fig. 67-33).

FIGURE 67-32 A, Contrast-enhanced, cardiac gated CT image (soft tissue windows) shows an angiosarcoma within the right atrial myocardium (arrows), which contains punctate areas of marked enhancement compatible with highly vascular tumor components. B, There is neoplastic involvement of the pericardium, which is studded by multiple, prominently enhancing nodules (arrowheads) and contains pericardial effusion.

(Courtesy of Tan-Lucien Mohammed, MD, Cleveland Clinic.)

FIGURE 67-33 Angiosarcoma in a 33-year-old man with a 1-month history of hemoptysis and dyspnea. A, Contrast-enhanced coned CT image (soft tissue windows) shows an enhancing, oblong mass within the right atrial wall (arrows). Note diffuse enhancement of the pericardium surrounding a moderate pericardial effusion. B, Axial CT image (lung windows) reveals widespread pulmonary nodules with halos of ground-glass density, compatible with hemorrhagic metastases.

Magnetic Resonance Imaging

Angiosarcomas are typically infiltrative masses in the right atrial myocardium that when compared with myocardium are isointense with higher signal intensity areas (owing to focal hemorrhage) on T1-weighted MRI, isointense on T2-weighted sequences, and heterogeneous with areas of high intensity on cine MRI (Fig. 67-34). These tumors tend to show strong, heterogeneous enhancement after contrast administration; this is termed a “sunray” appearance if pericardial tumor infiltration also enhances.^8,10

FIGURE 67-34 Right atrial angiosarcoma in a 35-year-old woman. A, Contrast-enhanced axial CT scan (soft tissue windows) shows a large, heterogeneously enhancing mass (arrows) filling the right atrial chamber. B, Coronal T1-weighted MR image shows multiple areas of high signal intensity within the mass (arrows), consistent with hemorrhagic foci. C, Gross specimen photograph shows the mass (arrows) in identical orientation to B. There are several areas of purple hemorrhagic material within the tumor. Note nodular metastatic deposits within the pericardium (arrowheads).

Differential Diagnosis

The differential diagnosis of a right atrial mass includes thrombus, metastatic disease, liposarcoma, angiosarcoma, an unusual right-sided cardiac myxoma or fibroma (both tend to calcify), and PCL.⁵⁰ Aggressive features, such as a broad-based or intramural tumor configuration, infiltration of the pericardium, involvement of cardiac valves, and pulmonary metastases, all argue in favor of a malignant rather than a benign etiology. The presence of a hemorrhagic pericardial effusion is particularly supportive evidence of angiosarcoma.

Treatment Options

Surgery for cardiac sarcomas may be performed, but depends on tumor location, degree of local invasion, and presence of metastases at presentation. Surgical intervention ranges from open biopsy to palliative debulking to wide surgical resection.⁴⁹ Cardiac transplantation may be considered if the lesion is considered unresectable, excluding the presence of extracardiac metastases.⁵¹ Transplantation is not commonly done because of the high risk of local recurrence and immunosuppression-induced lymphoma (2% to 13% in cardiac allograft recipients).⁴⁹ Adjuvant chemotherapy or radiation therapy may provide limited benefit and may be used in patients with advanced (nonsurgical) disease, local tumor recurrence, or resections with positive tumor margins.^49,51

KEY POINTS: ANGIOSARCOMA

Cardiac angiosarcoma must be suspected in the setting of a right atrial mass with pericardial effusion, especially if the pericardial effusion is high attenuation (hemopericardium).

Cardiac angiosarcoma is the only differentiated cardiac sarcoma that chiefly arises in the right atrium (90%). Other cardiac sarcomas tend to arise in the left atrium, or do not have a site predilection.

Characteristic MRI features include focal high intensity areas on T1 (corresponding to areas of hemorrhage) and strong postcontrast enhancement (reflecting tumor vascularity).

Definition

Leiomyosarcomas account for 8% to 10% of cardiac sarcomas and are chiefly located in the posterior wall of the left atrium. Some tumors may represent the atrial extension of sarcomas arising within the pulmonary veins or venae cavae.^1,49 In 30% of cases, leiomyosarcomas are multifocal.⁸

Prevalence

Approximately 75% to 80% of cardiac leiomyosarcomas arise in the left atrium.¹ The male-to-female ratio is variably reported (4 : 2 vs. 5 : 7), and sexual predilection cannot be stated with certainty.¹ The mean age at presentation has been reported to be 37 years (range 20 to 61 years).¹

Pathology

Histologic features of cardiac leiomyosarcoma include intracytoplasmic glycogen, perinuclear vacuoles, blunt-end nuclei, fascicular growth at right angles, and cytoplasmic fuchsinophilia. The distinction between leiomyosarcoma and MFH at microscopic inspection may be difficult.¹

Manifestations of Disease

Differential Diagnosis

The differential diagnosis of a left atrial mass includes myxoma, thrombus, pulmonary venous extension of lung malignancy, leiomyosarcoma, osteosarcoma, MFH, and very rarely, paraganglioma.

Treatment Options

Surgical excision of the neoplasm may be attempted, ranging from debulking to attempted wide resection. Cardiac transplantation may be considered in advanced disease except when distal metastases are present.⁵¹ Adjuvant chemotherapy or radiation therapy may provide some benefit and is indicated in patients with advanced (nonsurgical) disease, local tumor recurrence, or resections with positive tumor margins.^49,51

KEY POINTS: LEIOMYOSARCOMA

Cardiac leiomyosarcomas typically (80%) arise in the left atrium, similar to osteosarcoma and MFH, and may mimic an atrial myxoma.

Almost one third of cardiac leiomyosarcomas are multifocal in the heart.

Definition

Cardiac sarcomas with osteosarcomatous differentiation arise almost exclusively (>95%) in the left atrium.^1,10 Osteosarcomas commonly involve the mitral valve.⁸

Prevalence

Osteosarcomas account for 3% to 10% of cardiac sarcomas.¹

Pathology

Grossly, cardiac osteosarcomas are typically large tumors (4 to 10 cm) almost uniformly located within the posterior left atrial wall.¹⁰ On cut section, they have a pale mucoid or gelatinous appearance with gritty components.⁶ Microscopic features include osteoid material and atypical osteocytes indistinguishable from skeletal osteosarcomas. Notably, these tumors are often pleomorphic and may contain areas of fibrosarcoma, chondrosarcoma, or giant cell tumor.⁶

Manifestations of Disease

Imaging Techniques and Findings

Radiography

No reports are available concerning specific radiographic manifestations of osteosarcoma, but the most common radiographic abnormality in cardiac sarcomas overall is cardiomegaly.⁵ In situations of significantly compromised pulmonary venous drainage, features of prominent septal lines and vascular congestion may develop on chest radiographs.

Ultrasonography

No reports are available concerning echocardiographic depiction of a cardiac osteosarcoma.

Computed Tomography

Calcification may be evident on CT images, but this is not a consistent feature of cardiac osteosarcoma.⁸ This neoplasm mimics a left atrial myxoma, but discerning features include invasion of adjacent structures, a broad base of attachment to the atrial wall, and lack of association with the fossa ovalis (Fig. 67-35A).⁸

FIGURE 67-35 Osteosarcoma in a 50-year-old woman who presented with chronic cough. A, Contrast-enhanced axial CT scan (soft tissue windows) shows a lobulated mass (arrow) in the left atrium with extension into, and expansion of, the right inferior pulmonary vein (arrowhead). B, T1-weighted axial MR images, before and after administration of gadolinium, show a lobulated left atrial mass (arrow) and pulmonary venous extension (arrowhead) with heterogeneous enhancement. C, Surgical specimen of opened left atrium shows a polypoid mass occupying the chamber with components of necrosis, hemorrhage, and cystic change.

Magnetic Resonance Imaging

Osteosarcomas are reported as heterogeneous and isointense when compared with myocardium on T1-weighted MR images, heterogeneous and hyperintense on T2-weighted MR images, and largely hyperintense on cine MRI. There is no consistent postcontrast appearance (Fig. 67-35B).⁸

Differential Diagnosis

The differential diagnosis of a left atrial mass includes myxoma, lung tumor invasion via a pulmonary vein, leiomyosarcoma, MFH, osteosarcoma, and rarely paraganglioma.

Treatment Options

Excision of the neoplasm should be attempted, ranging from palliative debulking to wide surgical resection. Cardiac transplantation may be considered, but is not indicated when distal metastases are present.⁵¹ Adjuvant chemotherapy or radiation therapy may provide some benefit and is indicated in patients with advanced (nonsurgical) disease, local tumor recurrence, or resections with positive tumor margins.^49,51

KEY POINTS: OSTEOSARCOMA

Cardiac osteosarcomas arise almost exclusively (>95%) in the left atrium.

Cardiac osteosarcomas only variably show calcification on radiologic imaging.

Histologic appearance of the tumor is essentially indistinguishable from cardiac metastasis of skeletal osteosarcoma, but metastatic osteosarcoma is usually deposited in the right atrium, whereas primary cardiac osteosarcoma arises in the left atrium.

Definition

Rhabdomyosarcoma is the most common subtype of cardiac sarcoma in children and young adults.^1,8 In contrast to other cardiac sarcomas, rhabdomyosarcoma shows no chamber predilection and does not tend to involve the pericardium.^1,27 This tumor is multifocal in 60% of patients, and is more likely than other sarcomas to involve a cardiac valve.^8,52

Prevalence

Rhabdomyosarcomas account for 4% to 7% of cardiac sarcomas. Mean age at presentation ranges from 14 to 30 years, which is decades younger than other sarcomas. Sexual predilection (male-to-female) is contradicted in separate case series (2 : 4 or 3 : 2) and is inconclusive.¹

Pathology

On gross examination, these tumors are located within the myocardium and tend to exhibit necrotic areas.⁸ Cardiac rhabdomyosarcomas are embryonal; the diagnostic feature on histologic examination is the presence of rhabdomyoblasts, best identified by periodic acid–Schiff positivity.⁶ Immunohistochemical staining to identify cells with muscle antigens (desmin and myoglobin) is necessary for diagnosis.¹

Manifestations of Disease

Imaging Techniques and Findings

Radiography

There are no specific manifestations of rhabdomyosarcoma described on chest radiography. Cardiomegaly is the most common radiographic feature of cardiac sarcomas.⁵ In situations of significantly compromised pulmonary venous drainage owing to tumor mass effect, features of prominent septal lines and vascular congestion may develop on chest radiographs.

Ultrasonography

Transesophageal or transthoracic echocardiography may reveal intramural involvement by rhabdomyosarcoma (solitary or multifocal), intracavitary extension, and the impact on an adjacent cardiac valve.⁵³

Computed Tomography

On CT, rhabdomyosarcomas are shown as solitary or multifocal intramural masses, often lower in density than normal myocardium.⁴⁹

Magnetic Resonance Imaging

Rhabdomyosarcomas are reported as isointense to myocardium on T1-weighted MRI, isointense or heterogeneous on T2-weighted sequences, and isointense on cine MRI (Fig. 67-36). These tumors tend to enhance heterogeneously after contrast medium administration, with focal nonenhancement in necrotic areas.^8,49

FIGURE 67-36 Rhabdomyosarcoma of the left ventricle in a 6-month-old girl status post resuscitation from cardiac arrest. A and B, T1-weighted axial (A) and coronal (B) MR images show a slightly hyperintense mass (asterisk) arising from the left ventricular myocardium. C, Resected specimen has the gross appearance of muscular tissue.

Differential Diagnosis

Primary cardiac rhabdomyosarcoma has no particular site predilection in the heart. The differential diagnosis includes right-sided and left-sided cardiac masses and tumors that may arise in multiple intracardiac sites such as metastatic disease, rhabdomyoma (in infants), leiomyosarcoma, and PCL in addition to rhabdomyosarcoma (in children and young adults).

Treatment Options

Excision of the neoplasm may be attempted, ranging from palliative debulking to wide surgical resection. In most patients, the tumor is advanced at presentation.⁵² Cardiac transplantation may be considered, but is excluded when distal metastases are present.⁵¹ This malignancy shows poor response to adjuvant radiation or chemotherapy.⁵²

KEY POINTS: RHABDOMYOSARCOMA

Rhabdomyosarcoma is the most common primary cardiac sarcoma in children and young adults.

Rhabdomyosarcoma has no site predilection in the heart and may be multifocal at presentation (60% of cases).

In contrast to most other primary cardiac sarcomas, pericardial involvement by rhabdomyosarcoma is unusual, but valvular invasion is common.

Definition

Liposarcoma is a rare histologic subtype of cardiac sarcoma and tends to arise in the right side of the heart.⁴⁹

Prevalence

Primary cardiac liposarcomas account for less than 1% of cardiac sarcomas. A liposarcoma metastatic to the heart occurs much more frequently than primary cardiac liposarcoma.³⁰

Pathology

Grossly, the tumor has a yellow, soft, and smooth surface with ill-defined margins often bulging into the right atrial or ventricular chamber.³⁰ Histologic features include atypical fat cells with malignant lipoblasts invading the adjacent myocardium.^1,30 On microscopic examination, liposarcomas may be easily confused with LHIS and pleomorphic MFH.¹

Manifestations of Disease

Imaging Techniques and Findings

Radiography

Chest radiography may be unremarkable, or the cardiac silhouette may be enlarged.⁵⁴

Ultrasonography

Echocardiography may show an echo-free space compatible with a fat-containing tissue mass, with or without intracavitary extension.⁵⁴

Computed Tomography

Foci of fat density may be evident on CT images (Fig. 67-37), but liposarcomas are also described as soft tissue masses without fat components.⁸ Areas of low-density necrosis or hemorrhage may be present within the tumor. CT may delineate myocardial, intracavitary, intravascular, or pericardial extension of tumor, and involvement of a cardiac valve (see Fig. 67-37).⁵⁴ Metastases to the lungs, bone, or brain may also be identified.³⁰

FIGURE 67-37 Primary cardiac liposarcoma in a 53-year-old woman with back pain. A and B, Cardiac gated contrast-enhanced axial (A) and coronal reformat (B) CT images show an infiltrative mass (arrows) within walls of the right and left atria that contains fat density (arrowhead). There is invasion of the inferior vena cava (asterisk). Note associated pericardial effusion.

Magnetic Resonance Imaging

Reports describe a heterogeneous appearance on MRI.⁸ In contrast to cardiac lipoma or LHIS, fat saturation sequences are not particularly helpful in diagnosing a cardiac liposarcoma.³⁰

Differential Diagnosis

The differential diagnosis of fat-containing lesions in the heart includes lipoma, LHIS (typically dumbbell-shaped and limited to the interatrial septum), and liposarcoma (which may have soft tissue components and features of local invasion). Right-sided cardiac masses that show aggressive features of intramural or intracavitary extension include metastatic disease, angiosarcoma, liposarcoma, and PCL.

Treatment Options

Excision of the neoplasm may be attempted, ranging from palliative debulking to wide surgical resection. Cardiac transplantation may be considered, but is not indicated when distal metastases are present.⁵¹ Adjuvant chemotherapy or radiation therapy may provide some benefit, and is indicated in patients with advanced (nonsurgical) disease, local tumor recurrence, or resections with positive tumor margins.^49,51

KEY POINTS: LIPOSARCOMA

Cardiac liposarcomas tend to arise in the right atrium.

Fat density is not always appreciated on radiologic imaging of cardiac liposarcoma, which may manifest as a heterogeneous soft tissue mass.

Metastatic liposarcoma to the heart is much more common than primary cardiac liposarcoma (<1% of cardiac sarcomas).

Definition

PCL is defined as an aggressive non-Hodgkin lymphoma involving exclusively the heart or pericardium or both, or a non-Hodgkin lymphoma with most of the tumor located within the heart.⁴⁹ PCL tends to develop in immunocompromised patients.⁴⁹

Prevalence

PCL is rare, with an incidence of 0.056% in one large autopsy series.⁵⁵ PCL represents 1.3% of primary cardiac tumors and 0.5% of extranodal lymphomas.⁵⁵ Approximately 50% of reported cases are in immunocompromised patients, including patients with human immunodeficiency virus (HIV) infection or allograft transplant.¹ There is a slight male predominance.¹⁰

Pathology

On gross examination, PCL appears as multiple firm, whitish nodular lesions centered in the myocardium or epicardium, often with pericardial infiltration. The right atrium and ventricle are both involved in 75% of cases.¹⁰ PCL is less likely than a cardiac sarcoma to show necrotic zones, or valvular or intracavitary invasion.^1,8 Virtually all PCLs are high-grade B cell lymphomas.^1,6 Immunohistochemical staining is typically positive for common leukocyte and L26 antigens (specific for B cell lymphoma).⁴⁹ Most PCLs in immunocompromised patients contain Epstein-Barr virus DNA.^1,6 Cytology of the pericardial fluid is diagnostic for PCL in 67% of cases.

Manifestations of Disease

Imaging Techniques and Findings

Radiography

Cardiomegaly and signs of pulmonary edema may be evident when a pericardial effusion is present (Fig. 67-38).^5,56

FIGURE 67-38 A 47-year-old HIV-positive man with cardiac tamponade. Pericardiocentesis confirmed non-Hodgkin lymphoma. A, Frontal chest radiograph shows enlargement of the cardiac silhouette. B and C, Coronal reformat (B) and axial (C) contrast-enhanced CT images show a large pericardial effusion exerting critical mass effect on the heart, including bowing of the interventricular septum (arrow), consistent with tamponade.

Ultrasonography

Echocardiography may reveal hypoechoic masses of the right atrium and ventricle, pericardial effusion, and, occasionally, diastolic collapse of the right heart chambers when cardiac tamponade is present.^5,56

Computed Tomography

PCLs are multinodular, intramural masses located in the right atrium and ventricle, characteristically with pericardial thickening, nodularity, or effusion (Figs. 67-39 and 67-40).^10,49 The pericardial effusion may be quite large.¹⁰

FIGURE 67-39 PCL (large B cell) in a 73-year-old woman who presented with a 2-month history of fatigue and anasarca. A, Contrast-enhanced coned axial CT image shows a multilobulated soft tissue mass infiltrating the interatrial septum and atrioventicular septum. Note polypoid intracavitary extension (arrows) and pericardial involvement (arrowhead). B, Gross autopsy photograph confirms expansion of the interatrial septum by an infiltrative, pale yellow soft tissue mass (asterisk). Note the polypoid projections into the left atrial chamber (arrows).

FIGURE 67-40 PCL (anaplastic large cell lymphoma) in a 29-year-old pregnant woman with chest pain. Contrast-enhanced axial CT image shows a homogeneous oval mass arising from the posterior left ventricular wall (arrows) and a moderate-sized pericardial effusion. Autopsy confirmed extensive nodularity of the pericardium compatible with contiguous lymphomatous involvement.

Magnetic Resonance Imaging

PCLs manifest as nodular or infiltrative lesions that are isointense or hypointense on T1-weighted MRI and hyperintense on T2-weighted sequences (Fig. 67-41). Postcontrast images may show homogeneous or heterogeneous tumor enhancement.^8,49 Delayed enhancement imaging (with inversion times to null myocardium) may improve delineation of the tumor.¹⁰

FIGURE 67-41 PCL (non-Hodgkin) in a 74-year-old man with pericardial effusion. A, Contrast-enhanced axial CT image shows wide-based right atrial mass (asterisk) with probable extension into the posterior left atrial wall (arrow). B, T2-weighted axial MR image more clearly delineates hyperintense intramural tumor extending within the left atrial wall (arrow).

Differential Diagnosis

The differential diagnosis of multifocal cardiac masses (with or without pericardial effusion) includes metastatic disease to the heart (including leukemia and secondary cardiac lymphoma), leiomyosarcoma, rhabdomyoma/rhabdomyosarcoma (in younger patients), and PCL.

Treatment Options

When superior vena caval obstruction develops because of tumor bulk, it may be treated surgically or with metallic stents. In contrast to other cardiac malignancies, gross resection is not indicated in most cases of PCL.⁴⁹ Randomized trials have shown prolonged survival and reduction of cardiac symptoms with the use of chemotherapy (including anthracycline-based agents), either alone or followed by field radiation.⁵⁵

KEY POINTS: PRIMARY CARDIAC LYMPHOMA

PCL is a B cell lymphoma limited to the heart or pericardium or both, and is even rarer than primary cardiac sarcomas.

PCL is associated with immunosuppressed conditions (including HIV-positive or post-transplant patients).

PCL tends to arise in multiple sites and often manifests clinically as congestive heart failure with significant pericardial effusion.