This 10 year old female presented with a pigmented papule on her vulva. A subset of genital nevi look unremarkable clinically but have atypical histologic features. This is well-described in the literature. Genital nevi include those on the labia, mons, perineum, penis and scrotum. The histologic features may mimic nodular melanoma. Often times, these nevi have large expansile nests, located at all positions along the retia. There is typically loss of cellular cohesion. There may be cytologic atypia, both epidermally and dermally. Rare mitoses may even be observed. Because it is rare for premenapausal women to develop vulvar melanoma, these features should be heavily scrutinized and the lesion excised if in doubt [J Cutan Pathol 2008;35:889-898].
At low power, the epidermis is acanthotic and papillomatous. Thre is a cellular nevomelanocytic lesion, involving the epidermis and dermis. There is overall symmetry.