Melanocytic Nevi of Special Sites

Special site nevi or nevi with site-related atypia are terms used to describe melanocytic nevi located in some anatomic regions that, although benign, show unusual or atypical microscopic findings that may lead to diagnostic confusion with melanoma. A number of special sites have been proposed, including the ear, acral skin, genital region, the breast, and scalp. One may also include nevi of flexural sites and umbilical melanocytic nevi in this group. While anatomic site likely factors as a parameter for altered growth patterns of melanocytes when the cutaneous microanatomy is different, and/or the site more subject to repetitive trauma, as in the case of acral nevi, the proposed influence of anatomic region to the architecture of a melanocytic nevus is largely speculative and the designation “special site nevus” may be overused by pathologists, as there is significant overlap in the appearance of what nevi can look like at almost any site.