[Aneurysm of a saphenous vein bypass graft to coronary artery: a case report discovered as an incidental finding].

We report a case of aortocoronary bypass graft aneurysm revealed by exertional dyspnea and presenting as an anterior mediastinal mass at the unenhanced computed tomography scan. The diagnosis has been established using combined contrast-enhanced CT scan which specified the vascular nature of the mass and coronary angiography which connected it to the aorto-marginal branch saphenous vein graft. This case illustrates the frequently asymptomatic expression of aneurysm and the importance of combined imaging modalities for the diagnosis.