Mediastinal Lymphadenopathy

Lymphadenopathy represents the pathologic enlargement of lymph nodes. Within the chest, the mediastinum is the most commonly affected region. Mediastinal lymphadenopathy may result in loss of normal mediastinal contours or thickening of lines and stripes. On computed tomography (CT), lymph nodes measuring greater than 1 cm in short-axis dimension are typically considered enlarged. Although many disease process may result in mediastinal lymphadenopathy, including lymphoma, metastatic disease, infections, and sarcoidosis, specific characteristics such as attenuation, enhancement, and calcification help narrow the differential diagnosis. PET/CT demonstrates the metabolic activity of structures such as lymph nodes and may help in identifying pathologic lymphadenopathy. However, PET/CT cannot reliably differentiate between lymphadenopathy due to active malignancy and certain benign processes such as active infection or sarcoidosis.