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This paper is a review of 120 cases of primary malignant melanoma of the oral cavity occurring in the Japanese. We have collected 18 cases from our own department and the remainder from the literature. Since malignant melanoma arising from the oral mucosa and ectopic pigmentation are relatively common in Japan, an assumption has grown as to a possible relationship to histogenesis. The analysis of the material and the discussion are focused on these points. Malignant melanoma of the oral cavity is not rare in the Japanese. Some of the cases do not seem to have any relation to oral melanosis, but almost two‐thirds of the cases were found associated with it (36.2% of melanoma was associated with pre‐existing melanosis, and 29.8% with concurrent or later‐developing melanosis). The biological behavior and histologic patterns of these melanoses were similar to those of lentigo maligna of the skin. The pre‐existing melanoses seemed to be the most common precancerous lesion of the oral mucosa as far as malignant melanoma was concerned.

The effects on plasma lipids of daily intraperitoneal injections of 4mg of melatonin (N‐acetyl‐5‐methoxytrypt‐amine) for 10 27 day periods were examined biochemically and morphologically in rats fed regular and high‐cholesterol (1% cholesterol, 0.5% cholic acid) diets. Melatonin administration had no significant effect on plasma lipids and lipoproteins in the rats on a normal diet but blunted the effects of a high‐cholesterol diet on these parameters. No effects of melatonin on lipase activity were noted. Melatonin also diminished the fatty infiltration in the liver of animals on the high‐cholesterol diet. The high‐cholesterol diet produced major increases in VLDL and LDL cholesterol and protein content, and decreases in HDL cholesterol and protein. Melatonin decreased the extent of this plasma lipoprotein increase, although it did not completely prevent the phenomenon. Therefore, the effect is thought to be quantitative and not quantitative in nature. Acta Pathol Jpn 39: 613‐618, 1989.