(A) Angiogram of one of the cephalic arteriovenous malformations. The vascular tumor was embolized using an endovascular technique and was operated on. The specimen was used as starting material to obtain endothelial cells derived from the malformation. (B) Phase-contrast microphotographs of confluent HUVEC or (C) confluent AMEC grown on gelatin-coated plastic dishes (original magnification ×100).