Deep penetrating nevus is a distinctive melanocytic lesion that may simulate melanoma both clinically and histologically.
To review clinical and histologic features of deep penetrating nevi and discuss their differential diagnosis, especially regarding melanoma.
The literature on deep penetrating nevi is reviewed and supplemented by our experiences with deep penetrating nevi.
One or more disturbing histologic features may frequently be found in deep penetrating nevi, including asymmetry, plump but fairly regular nests of melanocytes in the dermis, cytologic atypia with some nuclear pleomorphism, a small to medium-sized eosinophilic nucleolus, absence of maturation, occasional presence of normal dermal mitoses, and a patchy mononuclear inflammatory cell infiltrate. Although unusual, such histologic features should not be regarded as a sign of malignancy in deep penetrating nevi.