Comparative aspects of melanoma and non-melanoma skin cancers in Japan.

A total of 279 patients with squamous cell carcinoma (SCC), 169 with basal cell carcinoma (BCC), and 91 with malignant melanoma (MM) were treated at Saitama Medical School and the National Cancer Center (NCC). This statistical study was done to compare an early period (1962-1972) and recent period (1973-1985). The yearly onset of melanoma patients increased 3.4 times and that of basal cell carcinoma increased 1.8 times, while the percent of squamous cell carcinoma patients decreased slightly. The male/female ratio was 1.6 versus 1.1 for basal cell carcinoma, 2.0 versus 1.7 for squamous cell carcinoma, and 1.7 versus 1.2 for malignant melanoma in the early versus late periods. The age distribution of malignant melanoma patients showed a sudden increase after 20, which peaked in the fifties in the late period, while an even distribution between 40 and 60 was found in the early period. The frequency of preceding diseases in squamous cell carcinoma was 8 times for actinic keratosis, 0.6 times for scars and 1.1 times for radiodermatitis. Absences of preceding diseases for the different malignancies in the early and later periods were 28% vs 43% of squamous cell carcinoma, 76% vs 86% of basal cell carcinoma, and 93% vs 97% of malignant melanoma. The number of squamous cell carcinoma and malignant melanoma on the head and neck increased 1.2 times and 4.5 times, respectively. The frequency in each disease was 46.0% for squamous cell carcinoma and 11.1% for malignant melanoma. Palmo-plantar-subungual melanoma (PPSM) was seen in 40.7% and 34.5%.