Heterogeneity of primary malignant melanomas in oral mucosa: an analysis of 43 cases in Japan.

In contrast to Caucasians, Japanese people have a relatively high incidence of malignant melanoma in the oral cavity and volar-subungual skin. The classification of oral melanoma has not been established. We report 7 new cases of oral melanoma, with a review of 36 cases, published in Japan, between 1970 and 1984. Most of the cases reviewed have radial growth phases, and their gross and microscopic features seem to correspond to those of acral lentiginous melanoma of the skin. However, 1 of our cases and 3 previously reported cases of oral nodular melanoma suggest the presence of melanoma heterogeneity in the oral cavity.