Angiosarcoma with dermal melanocytosis

We report a case of angiosarcoma and dermal melanocytosis occurring simultaneously in the same lesion. We examined the primary and 2 metastatic lesions. Histopathologically, the anaplastic angiosarcoma cells had a tendency to form irregularly shaped small cavities. Immunohistochemically, they were strongly reactive with Ulex europaeus agglutinin (UEAI) stain. The mid and deep dermis of the same lesion had spindle or elongated slender melanocytes containing melanin granules. The melanocytes were positive with S-100 protein stain. Ultrastructurally, pinocytotic vesicles, fine filaments, and Weibel-Palade body-like dense granules were observed in the cytoplasm of angiosarcoma cells. Dermal melanocytes had external lamina and melanosomes in various stages. The melanocytes showed no similarity to the neoplastic tumor cells and there was no apparent intermediate form between the 2 kinds of cells. The etiological implications of dermal melanocytosis with a tumor of vascular origin are discussed.