Solitary aneurysm of the innominate vein.

Two cases of isolated saccular aneurysms of the innominate vein are presented that appeared as mediastinal masses. Contrast-enhanced computed tomography (CT) allowed for accurate diagnosis in one patient, while the second patient had atypical CT findings that led to thoracotomy for proper diagnosis. A diagnosis of innominate vein aneurysm should be considered when a uniform attenuation mediastinal mass is seen on CT so that unnecessary biopsy and surgery can be avoided.