Aneurysmal cyst, bone type, primary in an artery.

An aneurysmal bone cyst-like reaction involving the left common carotid artery bifurcation in an otherwise healthy 7-year-old boy is described. The patient presented with a 6-week history of an enlarging pulsatile neck mass. The mass was excised with connection of arteries on either side with a saphenous vein graft. There were no associated intracranial arterial aneurysms or associated skeletal lesions. A history of trauma could not be elicited. To the best of our knowledge this is the first report of an aneurysmal cyst, bone type, involving a large blood vessel.