[Cancers of the skin, relations to ultraviolet rays].

There are three main types of skin cancers: basal cell carcinoma, squamous cell carcinoma and melanoma. They are very different in terms of clinical presentation, evolution, and prognosis. Their frequency is increasing and there is sufficient evidence for the aetiological role of solar ultraviolet radiation (UVR). This evidence is based largely on epidemiological studies, animal models and studies of xeroderma pigmentosum patients. The risk of squamous and basal cell carcinoma increases with chronic solar exposure while the risk of melanoma seems to be more influenced by intermittent exposures. The physiopathological mechanisms of UV carcinogenesis are not yet entirely understood. One of the main factors seems to be mutagenesis due to impaired DNA photoproducts repair. Alteration in immune function and genesis of free radicals induced by exposure to UVR may also play a central role in UV carcinogenesis.