Malignant melanoma in the oral region: ultrastructural and immunohistochemical studies.

Malignant melanoma in the oral region is reviewed in its clinicopathological aspects. Clinically the melanomas were classified into five types; however, there were no histopathological differences according to these clinical types. Electron microscopic observation of the melanomas and primary culture cells derived from oral malignant melanoma revealed that, in patients whose prognoses were relatively good, many mature-stage melanosomes were found. Immunohistologically, there was a positive reaction for transferrin receptor and the expression of pRb2/p130 was found in only 2 of 13 patients, who are still alive after periods of over 14 years. The radiosensitivity of a cell line derived from human oral malignant melanoma was greater than that in cell lines derived from human cutaneous melanoma and with radiation, the number of melanosomes increased. There are very few clinical cases of oral malignant melanoma and very few cell lines derived from oral malignant melanoma, and so findings in these patients and these cell lines should be accumulated in order to clarify the biological behavior of oral malignant melanoma.