Dysplastic melanocytic nevi of the lower leg: sex- and site-specific histopathology.

Site-specific histopathology features have been reported for acral, auricular, flexural, and genital melanocytic nevi, however, to the best of our knowledge, site- and sex-specific histology of dysplastic nevi on the lower leg (between knee and ankle) of women (DN-LW) has not been reported. In this retrospective histopathology study, we compared DN-LW (N = 42) with appropriate control groups of (1) DN of the lower leg of men (N = 20; DN-LM), (2) DN from the back of women (N = 20), (3) common nevi of the lower leg of women (N = 40), and (4) levels 1-2 superficial spreading melanoma of the lower leg of women (N = 20). Compared with dysplastic nevi on the back, DN-LW were smaller in diameter and exhibited a significantly higher score for pagetoid spread (P < 0.05). DN-LW compared with DN-LM showed sex-specific differences with (1) pagetoid spread (P < 0.05), (2) cytologic atypia (P < 0.05), (3) presence of large melanocytes (P < 0.05), and (4) band-like pigmentation in the dermis underlying the nevus (54% in DN-LW vs. 15% in DN-LM). As with other body sites, the dermatopathologist should be aware that dysplastic nevi occurring on the lower leg in women have site- and sex-specific features. Knowing this profile may lower the risk of misdiagnosing DN-LW and melanoma of the lower leg of women.