Mediastinal distortions from focal masses: a CT and radiographic study.

Fifty-seven mediastinal masses were studied by computed tomography (CT) and chest radiographs to determine how their specific site of origin affected their direction of expansion and the distortion of contiguous structures. Forty-four masses arose anterior to the heart and great vessels (precardiovascular compartment). When these masses arose on the right, they extended posteriorly only as far as the coronal plane of the trachea. Left-sided masses were not similarly limited in their posterior extension. Thirteen masses arose around the trachea and esophagus or in the subcarinal space (tracheoesophageal compartment). Masses in the upper part of this compartment caused tracheal and great-vessel displacement. The mobile superior vena cava (SVC) was more often distorted than was the aortic arch. Subcarinal masses always expanded to the right, displacing the right lower lobe. The heart and great arteries were more resistant to displacement and distortion than were the systemic veins. The trachea and mediastinal bronchi were intermediate in their displacement. The hila were effective barriers to the expansion of mediastinal masses.