Epidemiology of melanoma and nonmelanoma skin cancer--the role of sunlight.

Melanoma and nonmelanoma skin cancer (NMSC) are now the most common types of cancer in white populations. Both tumor entities show an increasing incidence rate worldwide but a stable or decreasing mortality rate. The rising incidence rates of NMSC are probably caused by a combination of increased sun exposure or exposure to ultraviolet (UV) light, increased outdoor activities, changes in clothing style, increased longevity, ozone depletion, genetics and in some cases, immune suppression. A dose-dependent increase in the risk of squamous cell carcinoma (SCC) of the skin was found associated with exposure to Psoralen and UVA irradiation. An intensive UV exposure in childhood and adolescence was causative for the development of basal cell carcinoma (BCC) whereas for the aetiology of SCC a chronic UV exposure in the earlier decades was accused. Cutaneous malignant melanoma is the most rapidly increasing cancer in white populations. The frequency of its occurrence is closely associated with the constitutive colour of the skin and depends on the geographical zone. The highest incidence rates have been reported from Queensland, Australia with 56 new cases per year per 100,000 for men and 43 for women. Mortality rates of melanoma show a stabilisation in the USA, Australia and also in European countries. The tumor thickness is the most important prognostic factor in primary melanoma. There is an ongoing trend towards thin melanoma since the last two decades. Epidemiological studies have confirmed the hypothesis that the majority of all melanoma cases are caused, at least in part, by excessive exposure to sunlight. In contrast to squamous cell carcinoma, melanoma risk seems not to be associated with cumulative, but intermittent exposure to sunlight. Therefore campaigns for prevention and early detection are necessary.