Retiform haemangioendothelioma.

A case of retiform haemangioendothelioma (RH), a recently described rare cutaneous low-grade angiosarcoma, is presented. A 75-year-old female had a 3.5 cm cutaneous nodule in her right lower thigh with 10 year preoperative duration. Microscopically, the dermis and subcutis contained a diffuse and infiltrative neoplasm which was characterized by long arborizing blood vessels arranged in a retiform pattern lined by cuboidal and flattened cells, occasional hobnail appearance of endothelial cells, and a prominent small lymphocytic infiltrate. Small solid areas were also found. Neither significant cellular atypia nor mitotic activity was observed. Immunohistochemically, the tumour cells reacted with endothelial markers (CD31, CD34, factor-VIII-related antigen) and bound Ulex europaeus agglutinin 1. There was no pericytic component within the tumour. The tumour was diploid by flow cytometry. The patient had a local recurrence 27 months after the excision. These findings support the view that RH is a low-grade angiosarcoma and indicate that RH must be distinguished from conventional angiosarcoma.