Spindle cell hemangioendothelioma: an immunohistochemical and flow cytometric study of six cases.

Six cases of spindle cell hemangioendothelioma (SCH) are presented with immunohistochemical and flow cytometric analyses. One case was associated with Maffucci's syndrome. All lesions were solitary or multifocal in the extremities, and prepresentation duration ranged from years to decades. One case recurred but none had metastases. Histologically, in four of the six cases the main lesions appeared to arise within vessels, predominantly muscular vessels. All lesions consisted of cavernous hemangioma-like areas and solid cellular areas resembling Kaposi's sarcoma. Cellular atypia was minimal. At the periphery of the lesions, a cluster of large thick or thin walled, and probably malformed, vessels were observed. Immunohistochemically, factor-VIII related antigen, CD34, vimentin, and lectin binding Ulex europaeus agglutinin 1 stained endothelial cells lining vascular channels, and vacuolated, or epithelioid cells. Spindle cells in the solid areas were negative for these endothelial markers except for vimentin, but showed divergent positive immunoreactions of HHF35, alpha-smooth muscle actin, desmin, and collagen type IV. Five cases were diploid and one was aneuploid. There was no significant correlation among DNA ploidy, S-phase fraction, and local recurrence in SCH although the number of cases examined was small. These results suggest SCH may be a benign lesion, probably a reactive process, rather than a low-grade angiosarcoma.