Left innominate vein aneurysm: diagnostic imaging and pitfalls.

Thoracic venous aneurysms are very rare. They may be asymptomatic and can be found incidentally during imaging. They are associated with few complications including pulmonary embolism, rupture, and venous obstruction. Accurate diagnosis of a mediastinal aneurysm is essential to avoid complications secondary to biopsy or surgical intervention. This is a rare case of left innominate vein aneurysm, its imaging, as well as associated imaging shortfalls.