EPIDEMIOLOGY OF ATYPICAL MELANOCYTIC NEVI - AN ANALYTICAL STUDY IN A MEDITERRANEAN POPULATION

Atypical naevi are markers for increased risk of malignant melanoma, p roviding 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 a ttention to the role of sunburn. After adjusting for age, sex and year s of formal education, the presence of atypical naevi was significantl y 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 ma intained by also taking into account the sun sensitivity, expressed as phototype, as a confounder (OR = 1.5; 95% CI, 1.0-2.0). Concerning ph enotypical features, an increased risk of having atypical naevi was fo und for all the parameters included in so-called `fair complexion', ie blue eyes, blond or red hair, fair skin, phototype I-II, and a tenden cy to freckle. The greatest difference between subjects with and witho ut atypical naevi related to the number of common melanocytic naevi: m ore 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 e ntered in the multivariate model that best predicted the risk of atypi cal naevi, were: young age, male sex, high educational level, presence of a large number of common naevi, phototype I-II, and a history of p ainful sunburn. In conclusion, the variables predicting the risk of de veloping atypical naevi in Mediterranean people are identical to those observed in predominantly fair-skinned populations. The aetiologic ro le of sunlight has been pointed out and shows a statistically signific ant relationship between frequent sunburn and the development of atypi cal naevi also after controlling for the subject's phototype.