Number of nevi at a specific anatomical site and its relation to cutaneous malignant melanoma.

The risk of cutaneous malignant melanoma (CMM) is strongly associated with total number of nevi. Scanty information is available on the association between CMM at a specific anatomical site and number of nevi at the same site. We analyzed data from a case-control study conducted in Italy between 1992 and 1994, on 542 cases of CMM and 538 hospital controls. Cases and controls were examined by trained dermatologists who counted the number of melanocytic nevi. We derived multivariate odds ratios (ORs) and 95% confidence intervals (95% CIs) of site-specific risk of CMM for high versus low number of nevi at the corresponding site. The ORs of CMM for the highest versus the lowest tertile of number of nevi at the corresponding site was 1.4 (95% CIs: 0.7-2.8) at face and neck, 2.3 (95% CIs: 1.1-4.9) at anterior trunk, 4.9 (95% CIs: 2.9-8.4) at posterior trunk, 2.9 (95% CIs: 1.2-6.6) at upper limbs and 5.0 (95% CIs: 2.9-8.5) at lower limbs. In a case-case analysis, comparing CMM cases at a specific site and CMM cases at all other sites, the only excess risk was found for the posterior trunk, the ORs being 2.1 (95% CIs: 1.2-3.6) for the highest versus the lowest tertile of number of nevi. Our data do not support the hypothesis of a specific effect of nevi at each single anatomical site.