Naevi as a risk factor for basal cell carcinoma in Caucasians: a Danish case-control study.

The number of melanocytic naevi in Caucasians is related to previous exposure to the sun and is a well-documented major risk factor for cutaneous malignant melanoma. Basal cell carcinoma, which is the most common form of skin cancer, has also been shown to be related to exposure to the sun. To investigate whether the number of common naevi is a risk factor for basal cell carcinoma in Caucasians we performed whole-body counting of naevi > or =2 mm in a Danish case-control study with 145 cases of primary basal cell carcinoma and 119 controls matched on age, gender and place of residence. Naevi were recorded according to size and body region and the skin phototype was assessed. There was no correlation between self-reported skin type and the number of naevi. Females with basal cell carcinoma had more naevi than did female controls (median number of naevi: 65 and 32, respectively) while males with basal cell carcinoma did not differ from male controls (median number of naevi: 48 and 43, respectively). Female cases had more small size naevi (2 mm), intermediate size naevi (3-4 mm) and large size naevi (> or =5 mm) than did female controls. Females with basal cell carcinoma had a substantially higher number of naevi on the arms and the legs than did female controls, but also had more naevi on the trunk. For females, the risk for basal cell carcinoma increased with increasing number of naevi. Naevi were not a risk factor for basal cell carcinoma in males.