Statistical study on malignant melanoma in Japan (1970-1976).

The authors reported in 1972 a statistical study based on 501 cases of malignant melanoma. As continouous study this review was carried out on 456 cases of melanoma which were reported during six years between 1970 and 1976. These two studies showed quite similar results as follows: (1) Yearly incidnece of malignant melanoma indicated a definite upward trend and the average number of patients was 71.1 per year. (2) Distribution by age showed one peak in the seventh decade. (3) Sex ratio was 1.1: 1. (4) The number of cases per total population in Japan showed great increase in over fifth decades and two peaks in the 7th and 8th decades. (5) Average age of the onset of all melanoma was 51.6 years old, while, that of brain and spinal cord melanoma was 25.4 years old. In the skin melanoma with preexisting pigmented skin lesions, the median age of the onset of primary melanoma on the foot was 38.7 years old and that of originated melanoma except foot was 65.9 years old. (6) Incidence of the melanoma was high in the sole considering the number of melanocytes per unit skin area.