Pseudolymphomatous cutaneous angiosarcoma: a rare variant of cutaneous angiosarcoma readily mistaken for cutaneous lymphoma.

Cutaneous angiosarcoma is probably the most malignant neoplasm involving the skin. Three clinical variants of cutaneous angiosarcoma are recognized, including angiosarcoma of the scalp and face of elderly patients, angiosarcoma associated with chronic lymphedema, and postirradiation angiosarcoma. Histopathologically, these three variants of angiosarcoma show similar features, which consist of poorly circumscribed, irregularly dilated, and anastomosing vascular channels lined by prominent endothelial cells that dissect through the dermis. Focally, neoplastic endothelial cells show large, hyperchromatic, and pleomorphic nuclei, protruding within vascular lumina and creating small papillations. Usually, inflammatory infiltrate is sparse and consists of a patchy, perivascular lymphoid infiltrate around the neoformed vessels. In rare instances, cutaneous angiosarcomas may exhibit prominent inflammatory infiltrate, and the neoplasm may be mistaken for an inflammatory process, both from clinical and histopathologic points of view. We describe four examples of cutaneous angiosarcomas with dense lymphocytic infiltrates involving the neoplasm. Immunohistochemically, lymphocytes expressed immunoreactivity for CD3, CD5, and CD45 markers, whereas the germinal centers were positive for CD20, CD79a, and Bcl-6. The neoplastic endothelial cells expressed immunoreactivity for the CD31, CD34, podoplanin, Prox-1, Lyve-1, and D2-40. We discuss the possible relationship between neoplastic endothelial lymphatic cells and reactive lymphocytes. Cutaneous angiosarcoma with prominent lymphocytic infiltrate may be readily mistaken for cutaneous follicle center cell lymphoma or cutaneous pseudolymphoma.