Malignant epithelioid hemangioendothelioma of the colon. Report of a case.

Angiosarcoma of the colon with epithelioid and histiocytoid features, a malignant counterpart of epithelioid hemangioendothelioma, was observed in a 72-year-old man. The disease first manifested as a right cervical mass, with the histologic appearance of malignant, undifferentiated, large-cell epithelioid neoplasm. Light microscopy of the colonic tumor disclosed angiosarcoma, with active erythrophagocytosis and positive immunoperoxidase reactions to lysozyme, alpha-1-antitrypsin, and alpha-1-antichymotrypsin. Ultrastructural features of the tumor cells were those of intermediate between endothelial and histiocytic cells. The disease took a rapid fatal course with recurrence, peritoneal dissemination, and massive peritoneal hemorrhage. The cause remains unknown.