Hemangiopericytoma of the sigmoid mesentery: report of a case with immunohistochemical findings.

Hemangiopericytoma has been described in various sites in the body but only rarely in the mesocolon. This report describes the clinical course of an 83-year-old man whose mesosigmoidal tumor (hemangiopericytoma) was resected on 11 November 1994. Immunostaining was done with the following primary antibodies: alpha-actin, vimentin, factor VIII-related antigen, chromogranin, and S-100. Staining for factor VIII-related antigen was strongly positive in the endothelial cells of the capillaries, but negative in the tumor cells. The tumor cells contained immunoreactive vimentin, but demonstrated no alpha-actin, chromogranin, or S-100. Since the operation, the patient has been disease-free for 11 months.