Etiology and epidemiology of melanoma and skin neoplasms.

The incidence of malignant melanoma has increased five- to sixfold during the last 40 years in white populations. Recent epidemiologic investigations have disclosed intermittent, intense sun exposure as a major risk factor. Exposure in childhood seems especially noxious. Number of nevi is another independent risk factor, but characteristics such as irregular border, pigmentation, and accentuated skin margins did not have significant influence in a French hospital-based study. A Canadian survey including 1146 children suggests that the number of nevi may be related to previous intermittent sun exposure, as well as to other melanoma risk factors such as skin complexion, propensity to burn, and tendency to freckle. Recent research in nonmelanoma skin cancer corroborates current viewpoints of significant underreporting and genuinely increasing incidence rates, supposed to be caused by increased lifelong sun exposure due to changes in lifestyle.