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Objective: To investigate the impact of a surveillance program aimed at early diagnosis of melanoma in a cohort of subjects classified at risk on the basis of their number of nevi. To compare the number of observed cases of melanoma in the cohort to that expected number in the general population of the same area., Methods: Two hundred and eighteen subjects with no personal or family history of melanoma residing in the Florence district who showed more than 30 common acquired nevi and 3 or more atypical nevi (high-risk) have been followed for an average period of 3.4 years (range 1-6.5); an additional intermediate-risk group with 237 subjects was also enrolled., Results: Four incident melanomas were detected in 218 high-risk subjects followed for a total of 741.7 person-years; no melanoma was detected in the lower risk group. All the 4 detected melanomas were in situ (Clark level I), with an average interval since enrollment of 4.6 years (range 1.4-6.5). In accordance with age-and sex-specific incidence rates of melanoma (including in situ forms) in the general population of the area, the standardized incidence ratio (SIR) in the cohort was 44.1 (95% CI 16.5-117.5)., Conclusions: Subjects with more than 30 common nevi and 3 or more atypical nevi show about a 40-fold increased risk of developing melanoma. Even allowing for some degree of diagnostic anticipation due to periodic controls the risk appears higher than in the intermediate risk population. As a consequence of active follow up of individuals, all the detected tumors were at favourable prognosis. Periodic examination of these subjects should therefore be recommended as part of a prevention program for cutaneous melanoma in southern European populations.

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.