Malignant melanoma: dependence of site-specific risk on age.

Age-specific incidence of melanoma of the trunk and of the limbs increases slowly with age, while incidence of melanoma of the face increases rapidly. This observation has led to speculation that cumulative ultraviolet exposure determines risk for the face, while acute exposure affects the trunk and limbs. However, there have been strong secular trends in melanoma of the trunk and limbs, but not in melanoma of the face. Analysis of incidence data from Connecticut and Denmark shows that steadily increasing rates in successive birth cohorts account entirely for these secular trends and for the differences seen among the cross-sectional age curves of the various sites. Thus, incidence data do not support the hypothesis that melanoma of the face and melanoma of the trunk and limbs involve distinct pathogenic mechanisms.