RESUMEN
Cystic adventitial degeneration (CAD) of the arteries is an uncommon cause of intermittent claudication in adults. The majority of reported cases have involved the popliteal artery and have occurred predominantly in men, and all had clinical evidence of occlusive vascular disease. An unusual example of CAD of the common femoral artery masqueraded clinically as an aneurysm, but the arteriogram was normal. It involved 5 cm of the artery and half its circumference, and was resected and replaced with a saphenous vein graft. The cyst contained clear mucoid fluid and a fibrous wall without a cyst lining. This is the eighth case reported of CAD involving the proximal segment of a large lower extremity artery. The etiology is unknown, but many authors think such cysts arise from primitive "arthrogenic" mesenchyme in the adventitia of blood vessels.