Angiosarcoma of the spleen: a report of two cases and review of the literature.

Results of the ultrastructural study of one of two cases of splenic angiosarcoma established the blood vessel origin of this tumor. Fifty-three previously reported cases were reviewed. None of the 55 patients had a history of exposure to thorium dioxide, vinyl chloride, or arsenic, which are known to be associated with hepatic angiosarcoma and other tumors. A comparison of the splenic and hepatic angiosarcomas showed that tumors not associated with exogenous material frequently involve the spleen and liver simultaneously, and that tumors associated with thorium dioxide, vinyl chloride, or arsenic commonly involve the liver with sparing of the spleen.