Clinical and Histopathological Characteristics of Genital Melanocytic Nevi: A Report of 109 Cases and a Review of the Literature

Abstract

Melanocytic lesions on the genital area are rare and poorly documented; they occur more frequently on the vulva and less often on the perineum, pubic area, and male genitalia. Genital melanocytic nevi exhibit features similar to nevi occurring on other areas of the body; in addition, they display high clinical and histopathological variability and are mostly classified as common nevi. However, a benign subtype of genital nevi that occurs in young women is known as atypical melanocytic nevi. These nevi exhibit distinct morphological characteristics that sometimes overlap with those of cutaneous melanoma. A retrospective systematic review was performed of 111 biopsy specimens of pigmented lesions on the vulva, perineum, pubic area, penis, and scrotum collected between 1998 and 2009 to assess their clinicopathological characteristics. In this sample, there were 101 cases of common genital melanocytic nevi, two genital melanotic macules, seven atypical melanocytic nevi, and one dysplastic melanocytic nevus; no cases corresponded to cutaneous melanoma. Of the 111 patients, 14.4% were male, and 85.6% were female with a mean age of 34.3 years. The female exhibited a larger number of atypical melanocytic nevi than the males. The nevi displayed melanocytic proliferation, forming irregular and coalescent nests with a loss of cellular cohesion at several sites in the rete ridges. Cytologic atypia was mild to moderate. Difficulties in the histological interpretation of these lesions remain to this day; thus, diagnosis relies significantly upon the experience and subjective judgment of pathologists to distinguish morphologically between atypical genital nevi and melanoma.