Trends in nonmelanoma skin cancer in Japan.

We compared the prevalence of skin cancer and solar keratosis (SK) in patients who attended 26 Japanese university hospitals between 1976-1980 with those who attended between 1986-1990 to investigate whether the incidence of skin cancer has increased or not. Age-adjusted incidence rates of basal cell carcinomas (BCC) and SK, but not squamous cell carcinomas (SCC), from 1986-1990 were higher than those from 1976-1980. In addition, a population-based incidence study was conducted in Kasai City, Hyogo prefecture, to establish the frequency of skin cancer and SK. A total of 4736 people over 20 years of age were examined. Two BCC and 36 SK patients were identified clinically and histopathologically. SCC was not found. Age-adjusted incidence rates of BCC and SK per 100,000 were 16.5 and 486.1, respectively. The BCC incidence rate in Kasai City was significantly higher than the incidence of Japanese nonmelanoma skin cancer (NMSC) reported by Gordon in 1976. Further, subjects classified as skin type I showed statistically higher SK prevalence rates compared to skin types II and III. The present study indicates that the prevalences of NMSC and SK in Japanese have increased during the last three decades and that skin type I may be a risk factor for NMSC in Japanese.