Thoracic CT plays a major role in the evaluation of patients with suspected pulmonary malignancy. In particular, one major role for thoracic CT for patients with pulmonary malignancy is the depiction of hilar, mediastinal, and intrapulmonary lymph node enlargement. Correct identification and classification of lymph node locations is critical for accurate staging for lung cancer patients as well as numerous other thoracic diseases. Intrathoracic lymph nodes are commonly referred to in clinical practice using descriptive terms, although a widely accepted lymph node classification system, set forth by the American Joint Committee on Cancer (AJCC) and International Union Against Lung Cancer (UICC), is often used to standardize reporting of lymph node involvement in lung cancer patients. Although an extensive review of thoracic lymph node classifications is beyond the scope of this work, several images illustrating locations of abnormal lymph nodes in a patient with sarcoidosis will be reviewed. In this system, the designation “R” and “L” refers to “right” and “left” of midline, respectively.
Enlarged lymph nodes is seen just anterior and to the right of the trachea; this region is often referred to as the “right paratracheal space.” In the AJCC classification system, lymph nodes in this location are referred to as “upper paratracheal lymph nodes” (station 2); these lymph nodes lie inferior to the cranial margin of the left brachiocephalic vein, where this vein crosses anterior to the trachea, and superior to the cranial margin of the aortic arch.
A focus of high attenuation is present within the mildly enlarged right paratracheal lymph node; this high-attenuation focus represents calcification, which is a common occurrence in patients with sarcoidosis. In the AJCC lymph node classification, this lymph node is considered a “lower paratracheal lymph node (station 4).” This lymph node lies inferior to the cranial aspect of the aortic arch and cranial to the superior margin of the right upper lobe bronchus.