Rapid increase in diagnosis of cutaneous melanoma in situ in Sweden, 1968-1992.

We analyzed incidence trends of cutaneous melanoma in situ in Sweden in 1968-1992. Among men, age-standardized rates increased from 0.1/100,000 in 1968 to 2.9/100,000 in 1992, which corresponds to an average annual increase of 15.0%. Among women, rates increased from 0.3 to 3.7, and the annual increase was 12.8%. Age-specific rates increased since 1978, predominantly in men aged 45 years and older, whereas in women rates increased in all ages. Multivariate analysis showed that incidence rates could be explained by both cohort effects and period effects in addition to age. However, cohort effects seemed more important among men than among women, in whom period effects dominated. Thus, factors associated with the development of melanoma in situ may differ between the sexes. Melanoma in situ is an immediate precursor of invasive melanoma, and the increased detection and surgical excision of these tumors will prevent the occurrence of invasive melanoma.