Primary renal angiosarcoma: a case report with immunohistochemical, ultrastructural, and cytogenetic features and review of the literature.

Primary angiosarcoma of the kidney is a rare tumor for which fewer than 10 case reports appear in the English literature. A case of primary renal angiosarcoma is reported, in which the tumor showed poorly differentiated spindled sarcoma admixed with typical angiomatous differentiation. Antibodies against CD31, CD34, Ulex europeus lectin type I, factor VIII-related antigen, cytokeratin (AE1/AE3), vimentin, S100 protein, epithelial membrane antigen, carcinoembryonic antigen, desmin, and smooth muscle actin were examined. CD31 showed strong diffuse membranous staining of cells in the well-differentiated areas and strong membranous staining in the spindled, poorly differentiated areas. CD34 showed strong cytoplasmic and membranous staining in both the poorly differentiated and well-differentiated areas. Staining for factor VIII-related antigen and Ulex europeus was less intense and was limited to the well-differentiated areas. Staining for cytokeratin (AE1-AE3), S100, carcinoembryonic antigen, epithelial membrane antigen, desmin, and smooth muscle actin were negative. Electron microscopy showed spindle cells containing abundant pinocytotic vesicles, vimentin-type intermediate filaments, and rare Weibel-Palade bodies. A complex karyotype was found. Our findings suggest that CD31 and CD34 are useful in defining endothelial differentiation in poorly differentiated angiosarcomas in which reactions for Ulex europeus lectin type I and factor VIII-related antigen may be equivocal.