Angiosarcoma of the small intestine: an immunoperoxidase study.

A case of multifocal angiosarcoma of the small intestine is reported. These tumors often contain areas of solid sheets of cells and may be confused with poorly differentiated carcinoma or other sarcomas, as was the tumor in the reported case. Factor VIII-related antigen was demonstrated in biopsy samples by the peroxidase antiperoxidase method, showing the tumor to be an angiosarcoma. We conclude that the demonstration of factor VIII-related antigen in the neoplastic cells is an important aid in the diagnosis of angiosarcoma.