Abstract
A 52-year-old male presented with a perilimbal-epibulbar, flat, pigmented lesion of 7 months' duration. Microscopic evaluation disclosed a proliferation of intraepithelial dendritic melanocytes without frank atypia, a lesion formerly termed "primary acquired melanosis." Within the lesion there were also intraepithelial basal junctional nevocytic nests and occasional small subepithelial nevocytic clusters which were positive for MART-1, HMB-45, and SOX-10 and negative for Ki-67. This remarkable lesion was suggestive of dendritic melanocytes transforming into rounded nevocytes lacking dendrites. The embryologic and biologic implications of these findings are explored, notably in regard to the unusual acquisition in mature adults of common nevomelanocytic nevi.