Nevi of special sites.

Melanocytic nevi can have a wide range of histologic appearances. Within the spectrum of nevi, there exists a group that presents in certain anatomic locations with histologically worrisome features but nonetheless benign behavior. This group of nevi has been broadly categorized as nevi of special sites. The anatomic locations affected by this group include the embryonic milkline (breast, axillae, umbilicus, genitalia), flexural areas, acral surfaces, ear, and scalp. Nevi in these locations may be mistaken for melanomas because of their histologic appearance, resulting in inappropriate overtreatment of patients. In this article, the authors review the histologic features of these special site nevi and discuss the criteria that help distinguish them from melanoma.