Angiosarcomas of the skin.

Angiosarcomas of the skin develop almost exclusively in the following clinical settings: (1) the lymphedematous extremity, secondary to prior mastectomy in most instances; (2) the face and scalp, usually in elderly individuals; and (3) skin that has been previously radiated. Microscopically, there is a spectrum of architectural patterns. The best differentiated tumors exhibit obvious vascular spaces, which are lined by variably atypical endothelial cells, and that characteristically dissect between fibers of the reticular dermis. With proliferation of the atypical endothelial calls, vasoformative features are less evident, and there is often a syncytium of cellular bands composed of fusiform or spindled cells or, less commonly, cords, nests, and nodules of distinctly epithelioid cells. Overgrowth of the cellular elements can create seemingly patternless sheets of tumor. The foregoing architectural spectrum may be displayed in its entirety within a single biopsy specimen, and a multifocal distribution within the dermis is characteristic. Cytologic pleomorphism and mitotic figures are often obvious, but both criteria of malignancy may be essentially absent in the best differentiated fields. Ultrastructural observations consistently show differentiation toward endothelial cells and, in many cases, findings consistent with differentiation toward blood vessels. Both factor VIII-related antigen and Ulex europaeus lectin are reliable immunohistochemical markers. The outlook for patients with cutaneous angiosarcoma is poor, with a median survival of 20 months and a 5-year survival of 15%.