Angiomatoid melanoma.

Angiomatoid melanoma is a rare variant of malignant melanoma not currently recognized by the World Health Organization classification system. In this study, we present a case of primary angiomatoid melanoma in a 57-year-old man who presented to clinic with a complaint of a growing lesion on the frontal scalp for four months. Microscopic examination of the lesion revealed cavernous spaces filled with extravasated red blood cells. Immunohistochemical markers were positive for melanoma and negative for vascular endothelium. We also review the literature on angiomatoid melanoma, finding distinct morphological differences in previously reported cases. Owing to these differences, we propose new diagnostic criteria and offer a mechanism for formation of blood-filled cavernous spaces while cautioning against misinterpretation of CD31 expression by macrophages in zones of immune regression. Angiomatoid melanoma is a diagnostic challenge because of its rarity, signaling a need for further histopathological evaluation and more complete awareness of its features.