Abstract
A statistical study was made on 501 cases of malignant melanoma collected from Japanese literature from 1961 to 1970. Malignant melanoma is still found less in Japanese than in white racial groups but its incidence indicates a definite upward trend in recent years. The incidence of malignant melanoma according to sex is slightly higher in the male group than the female. The distribution of this disease by age presents no significant difference by sex and there are two high incidence peaks in the third and sixth decades in this series of study. The most frequent sites of involvement are the skin (28.5%), mucous membrane (27.0%) and eye (23.9%). In skin lesions, the most common primary site is the lower extremities, especially the sole of the foot. Among the mucous lesions, the mouth is the most popular site of involvement. The relationship between the onset of malignant melanoma and the number of the melanocytes in the different parts of the body has been studied. There seems to be a parallel relationship between the incidence of melanoma and the number of melanocytes per unit skin area. An exceptionally high incidence of melanoma was observed on the sole. The incidence of metastasis appears to be higher in the older age group than in the younger. There were high incidences of metastasis at the trunk, lower limbs and gastrointestinal tract. Fifty-five patients (63%) gave a history of preexisting pigmented lesions at the site of the primary melanoma.
