Immunohistochemical identification of factor VIII-related antigen in endothelial cells of cutaneous lesions of alleged vascular nature.

Immunohistochemical staining for factor VIII-related antigen (FVIII-RAG) with the peroxidase-antiperoxidase technic was used as a marker for endothelial cells in a variety of nevoid, reactive, and malignant vascular cutaneous proliferations. The endothelial cells of small normal cutaneous vessels gave the strongest reaction. The cells of hemangioma and angiokeratoma generally were stained, but with less consistency. In lymphangioma, pyogenic granuloma, and pigmented purpuric dermatosis, positivity was either patchy or of lesser intensity. Numerous strongly positive endothelial cells lining well-formed blood vessels were present in lesions of Kaposi's sarcoma, but the proliferating spindle cells forming "vascular slits" were uniformly negative. The cells of angiosarcoma were essentially negative, except for isolated elements in the better-differentiated areas. Plasma was also strongly positive; this may aid in distinguishing vascular from lymphatic channels. Anti-FVIII-RAG immunoperoxidase staining is a helpful aid in evaluating cutaneous vascular proliferations.