Immunohistochemical study of a pigmented nevus in the oral mucosa

A pigmented nevus is defined as a hamartomatous proliferation of nevus cells, and it is a most common skin lesion. Pigmented nevi of the oral mucosa are considered to a rare lesion with only a few cases being reported in Japan. Here, an intradermal nevus on the palate is described together with the results of immunohistochemical studies. A 44-yearold man had noted pigmentation and swelling of the palate for few years, but it was asymptomatic and not treated previously. The lesion was diagnosed to be an intradermal nevus histopathologically, and numerous melanocytic masses were seen in the connective tissue under the palatal epithelia. The melanin pigment stained with Masson-Fontana stain. Immunohistochemically, the following antibodies were tested: PoAb S-100 protein, MoAb S-100α, MoAb S-100β, MoAb or PoAb neuronspecific enorase (NSE), PoAb substance P, MoAb chromogranin A, keratin (MoAb K8.12, KL1), MoAb vimentin, and MoAb glial fibrillary acidic protein (GFAP). The melanocytes were positive to PoAb S-100 protein, MoAb S-100/β and MoAb vimentin.