Angiomatoid melanoma

초록

Unusual presentation of malignant melanoma may result in diagnostic difficulties. A paucity of melanin pigment, combined with an unusual histopathologic arrangement of neoplastic cells, may lead to diagnostic confusion. We described an unusual presentation of malignant melanoma that contained little melanin, but possessed prominent, large pseudovascular spaces filled with erythrocytes, imparting an angiomatoid histopathologic appearance suggesting vascular malignancy. A 64-year old previously healthy woman presented with palpable subcutaneous mass on her left buttock for 20 years. Recently the mass is slightly enlarged. The excised mass was not encapsulated and measured 2.1x1.6x1.0cm. The external surface is relatively smooth and circumscribed. The cut surface shows large blood filled cystic spaces and peripheral thin rim of grayish-tan soft tissue. Microscopically, the lesion revealed a large, blood-filled cystic space and peripheral area of sheets and nests of medium-sized polygonal cells having abundant amphophilic cytoplasm. A few cells showed intranuclear pseudoinclusion, and scanty, fine dust-like brown pigment with a few cells in mitosis. This cystic space was lined by single layer of flattened cells showing positivity for S-100 protein and HMB-45.