Malignant melanoma in Italy: risks associated with common and clinically atypical melanocytic nevi

Most epidemiologic studies on risk factors for cutaneous melanoma have been performed in predominantly fair-skinned populations.

Our purpose was to assess by means of a case-control study the importance of common melanocytic nevi (CMN) and clinically atypical nevi (CAN) as risk factors for cutaneous melanoma in a Mediterranean population.

One hundred six patients with invasive cutaneous melanoma and 109 population control subjects were included in the study. All subjects were younger than 70 years of age and were residents of the Florence area.

The adjusted odds ratios obtained by exact conditional analysis, accounting for age, sex, place of birth, and residence, were 2.6 (95 confidence interval [CI], 1.0 to 6.7) for 10 to 30 CMN, and 22.3 (CI, 4.8 to 215) for more than 30 CMN (chi 2 for trend, 25.41; p < 0.001), 2.9 (CI, 1.2 to 7.5) for large nevi, and 8.4 (CI, 2.2 to 31.4) for CAN. Tendency to freckle resulted in a twofold increase in risk (odds ratio, 2.2) (CI, 1.0 to 5.2). The relative risk associated with a large number of CMN was statistically significant after adjustment for all other variables. When adjusted for the number of CMN, none of the other variables showed a statistically significant increased risk.

A large number of CMN represents the most important risk factor for cutaneous melanoma in the Italian population. The presence of large nevi and CAN did not result in an increased risk when the number of CMN was considered.