Angiomatoid melanoma: a novel pattern of differentiation in invasive periocular desmoplastic malignant melanoma

A case of locally invasive, long-standing desmoplastic and amelanotic malignant melanoma is described in an 84-year-old man. Histologic examination of the involved periorbital tissue showed neoplastic foci exhibiting a novel pattern reminiscent of microvascular proliferation. These regions were characterized by malignant, S-100-positive tumor cells lining vessel-like spaces in transverse sections and forming tubuler-like structures in longitudinal sections. Recent data indicate that melanoma cells may express genes and patterns of differentiation in vitro akin to endothelial cells. Because angiosarcoma often involves facial and scalp skin of elderly individuals, awareness of angiomatoid differentiation in melanoma has important diagnostic implications. HUM PATHOL 31:1520-1522.