Occurrence of other malignancies in 1973 patients with basal cell carcinoma.

To evaluate the possible association of other malignancies with basal cell carcinoma, we reviewed 1973 consecutive patients with basal cell carcinoma. We searched the Swedish Cancer Registry for records reporting malignancies in the study population (1958-1984) and the expected number of malignancies was calculated on the basis of age- and sex-standardized incidence data. In 452 patients with basal cell carcinoma another malignancy was diagnosed. The expected number was 323 (relative risk = 1.4; 95% confidence interval = 1.3 to 1.5). A significant association with basal cell carcinoma was found in four cancer types for men and in three for women. For skin malignancies other than malignant melanoma there was more than a sixfold increased risk for men (relative risk = 6.8; 95% confidence interval = 4.8 to 9.4) and more than a threefold increased risk for women (relative risk = 3.1; 95% confidence interval = 1.4 to 5.9) during the period after the diagnosis of basal cell carcinoma. During the period before the diagnosis of basal cell carcinoma, there were also increased risks (men: relative risk = 5.0; 95% confidence interval = 3.1 to 7.5; women: relative risk = 4.0; 95% confidence interval = 1.9 to 7.4). This was in contrast to the risks of malignant melanoma. Before the diagnosis of basal cell carcinoma there was no significant increased risk of malignant melanoma but after the diagnosis there was more than a sixfold increased risk for men (relative risk = 6.8; 95% confidence interval = 4.8 to 9.4) and more than a fourfold increased risk for women (relative risk = 4.2; 95% confidence interval = 1.5 to 9.2).(ABSTRACT TRUNCATED AT 250 WORDS)