Introduction to Mediastinal Abnormalities

The mediastinum is the space between the pleura and lungs, extends from the thoracic inlet to the diaphragm, and contains various organs and structures that may be affected by a variety of disease processes including neoplasms, other acquired conditions and congenital anomalies. The abnormal mediastinum is typically initially identified on chest radiography because of a mediastinal contour abnormality or mass. The radiologist must assess the frontal chest radiograph to determine whether the lesion manifests as a focal, diffuse or multifocal mediastinal abnormality. The lesion must then be localized to a specific mediastinal compartment using the lateral chest radiograph. This allows the formulation of a focused differential diagnosis and recommendations for further evaluation and management that often involve contrast-enhanced chest CT and less frequently MRI. These studies allow further characterization of the lesion and identification of associated findings such as lymphadenopathy, skeletal involvement and locally invasive behavior. Cross-sectional imaging usually allows categorization of mediastinal abnormalities as vascular, surgical or non-surgical lesions. Benign pathognomonic conditions that do not require further treatment may also be confidently diagnosed.