Epidemiology of atypical melanocytic naevi: an analytical study in a Mediterranean population.

Atypical naevi are markers for increased risk of malignant melanoma, providing additional information about melanoma risk beyond that given by common melanocytic naevi. Little is known about the epidemiology of atypical naevi (AN), and available data are limited to predominantly fair-skinned populations. By using a case-control study that included 705 subjects with atypical naevi and 1,782 controls, we have analysed the aetiology of AN in a Mediterranean population, paying particular attention to the role of sunburn. After adjusting for age, sex and years of formal education, the presence of atypical naevi was significantly related to frequent sunburn before the age of 20 (odds ratio, OR, = 1.8; 95% CI, 1.3-2.5). Although less evident, this relationship was maintained by also taking into account the sun sensitivity, expressed as phototype, as a cofounder (OR = 1.5; 95% CI, 1.0-2.0). Concerning phenotypical features, an increased risk of having atypical naevi was found for all the parameters included in so-called 'fair complexion', i.e. blue eyes, blond or red hair, fair skin, phototype I-II, and a tendency to freckle. The greatest difference between subjects with and without atypical naevi related to the number of common melanocytic naevi: more than 30 common naevi were found in 41.5% of cases, but only in 9% of controls (OR = 8.0; 95% CI, 6.3-10.3). Overall, the six variables entered in the multivariate model that best predicted the risk of atypical naevi, were: young age, male sex, high educational level, presence of a large number of common naevi, phototype I-II, and a history of painful sunburn. In conclusion, the variables predicting the risk of developing atypical naevi in Mediterranean people are identical to those observed in predominantly fair-skinned populations. The aetiologic role of sunlight has been pointed out and shows a statistically significant relationship between frequent sunburn and the development of atypical naevi also after controlling for the subject's phototype.