Primary malignant melanoma of the oral cavity--its histological classification and treatment.

In contrast to Caucasians, the Japanese population has a relatively high incidence of malignant melanoma in the oral cavity, but its classification and treatment has not been established up to now. We present here the detailed clinical and histological features of 14 cases of oral melanoma. In 13 of the 14 patients, the lesions exhibited three phases: a nodular phase consisting of spindle-shaped or epithelioid tumor cells in the submucosa, a pigmented plaque phase consisting of preinvasive tumor cell nests in the lower epithelial layers, and a macular phase consisting of proliferation of dendritic melanocytes without apparent atypia or simple hyperpigmentation in the basal cell layer. The macroscopic and microscopic findings of 13 melanomas corresponded to those of acral lentiginous melanoma of the skin, while the one lesion showing no radial growth phase was classified as nodular melanoma. We devised a new treatment plan for oral melanoma in 1980, which includes surgical excision via an intraoral approach, therapeutic neck dissection, and adjuvant immunochemotherapy. Out of 11 patients treated in this manner, nine had a good outcome without major cosmetic and functional morbidity. This suggests that the prognosis of oral melanoma is not so poor as reported previously if adequate therapy is provided.