A tumor of medium-to-large veins, composed of plump-to-spindled endothelial cells that bulge into vascular spaces in a tombstone-like fashion. These tumors are thought to have "borderline" aggression, where one-third develop local recurrences, but only rarely metastasize. It is unclear whether the epithelioid hemangioendothelioma is truly neoplastic or an exuberant tissue reaction, nor is it clear if this is equivalent to Kimura's disease (see angiolymphoid hyperplasia with eosinophilia). (Segen, dictionary of Modern medicine, 1992)