A large mediastinal mass in a 43-year-old man was proven at thoracotom
y to comprise a right superior pulmonary vein aneurysm. Intraoperative
transesophageal echocardiography was useful in defining the abnormali
ty. Pulmonary venous aneurysm appears to represent an extremely rare b
ut surgically correctable addition to the differential diagnosis of mi
ddle mediastinal masses.