The series of cutaneous melanoma compiled by the Finnish Cancer Registry, a total of 2501 cases covering all tumors diagnosed in Finland in 1953-1973, was analysed. The age adjusted incidence was equal in both sexes (about 3.5/105 in the 1970s). The risk more than doubled during the study period. The most common locations of melanoma in males were the trunk (48%) and lower limbs (17%), and in females the lower limbs (36%) and the trunk (28%).
The age adjusted incidence rates were higher in urban areas than in rural districts and higher in southern parts of the country than in northern areas. However, after adjusting the rates for urban/rural residence of the population, the north south differences almost disappeared. In conclusion, the north south gradient was attributable to the degree of urbanization and not necessarily to the effect of latitude itself. Melanomas on the trunk in both sexes and those on the lower limbs in females had two features in common-the incidence of tumors on these locations increased markedly with time, and the age specific incidence rates increased sharply in middle age and levelled off thereafter. On the other hand, melanomas on the head and neck in both sexes and those on the lower limbs in males did not increase with time, and the risk was rather low in middle age and increased throughout life. The increase with time in the risk of melanoma could be accounted for by a cohort effect. These findings are not totally in accordance with the hypothesis of the association between sunlight and risk of melanoma, and it is concluded that recognition of sunlight as the only important risk factor of cutaneous melanoma may be an oversimplification of a complex problem.
Cancer 4 1 : 20 18-202 7, 1978. H E INCIDENCE OF MALIGNANT MELANOMA OF T the skin in different areas shows wide variation. High rates (4-16/105) have been reported e.g. from Australia, New Zealand, Norway, Sweden and Israel (Jews born in Israel), while India (Bombay), Japan (Miyagi), Puerto Rico and Singapore are examples of areas with low rates (< l/105). 1,5,8,37 In general, colored populations exhibit a low risk of cutaneous melanoma. However, tumors on the sole of the foot are common e.g. in Africans'? and native Puerto R i c a n ~. ~' The incidence in Finland is on an intermediate level among white population^.^^ Variation in incidence (or mortality) also oc-From the Finnish Cancer Registry, Helsinki,