Epidemiology and control of melanoma in white populations and in Japan.

In white populations living at moderate or low latitudes, melanoma has become one of the most common tumors in young adults. Epidemiologic studies show a complex association with sun exposure. Risk is related positively to the levels of exposure typical of the place of residence, and also to personally controlled exposure, with the maximum risk being related to acute intermittent exposure. Risk also varies with pigmentation, family history of melanoma, and the presence of benign and of dysplastic nevi. The following methods of control of melanoma in such populations are discussed: the most effective methods depend on early diagnosis; primary prevention appears difficult and requires evaluation; identification of very high-risk subjects on the basis of family history and dysplastic nevi will affect only a very small proportion of melanomas; the use of simpler methods to identify high-risk subjects is explored. In Japan, melanoma is comparatively rare, but increasing as rapidly as elsewhere. The incidence rate of acral lentiginous melanoma appears similar to that in whites, comprising a large proportion of melanoma in Japan. Control programs cannot be designed rationally, since basic information on the occurrence, presentation, and survival of melanoma in Japan is lacking. Some specific research questions are suggested.