Histopathological features of flexural melanocytic nevi: a study of 40 cases.

Melanocytic nevi in certain locations such as the genital and acral sites may have atypical histologic features simulating melanoma. We studied the microscopic findings of 40 melanocytic nevi of flexural sites (axilla, umbilicus, inguinal creases, pubis, scrotum and perianal area) to verify if flexural nevi show distinctive features similar to melanocytic nevi of the genital skin. The patients were young (mean age 20 years), the lesions were mostly removed for cosmetic reasons and we are not aware of any deaths or complications related to the removed nevi. We found that 22 (55.5%) out of 40 flexural nevi had "a nested and dyshesive pattern" similar to the melanocytic nevi of genital skin. This pattern was characterized by the confluence of enlarged nests with variation in size, shape and position at the dermo-epidermal junction and by the diminished cohesion of melanocytes. Dermatopathologists should pay attention to the "nested and dyshesive pattern" of flexural nevi that may mimick histologic changes of melanoma.