Indian Journal of Dermatopathology and Diagnostic Dermatology

Oral melanocytic nevi are localized developmental tissue malformations of nevus cells in the oral mucosa. Relatively rare in occurrence compared to their dermal counterparts, considerable debate exists in the literature related to their origin, development and maturation, and their relationship to oral melanocytes.We report two cases of oral melanocytic nevi with classical clinical presentation. The histopathology was consistent with the known patterns of oral melanocytic nevi. Special stains such as Masson Fontana, further substantiated the observation. S-100 and HMB-45 were applied to immunohistochemically elaborate the cell population. Interestingly two distinct cell populations were detected in the lesions. "Type A" cells in the center of the lesion were S-100 positive, indicating a neural origin and immaturity in development, while peripheral "type B" cells stained positive with HMB-45, indicating melanocytic origin and mature development.