Distribution of congenital melanocytic naevi and congenital naevus-like naevi in a survey of 3406 Italian schoolchildren

Background: Scanty information is available on the prevalence of congenital melanocytic naevi (CMN) and congenital naevus-like naevi (CNLN), particularly the small ones. Objectives: To estimate the prevalence of CMN/CNLN in Italian schoolchildren, and to assess variations according to potential risk factors for melanoma. Methods: We conducted a survey in 13 Italian areas on 3406 schoolchildren aged 12-17 years. Children were examined by dermatologists who assessed pigmentary traits and made a count of small (6-15 mm in diameter) and medium/large (> 15 mm) CMN/CNLN on 19 anatomical areas. Results: Overall, 592 children (17.4%) had one or more CMN/CNLN. Prevalence of small CMN/CNLN was 16.1%, and that of medium/large CMN/CNLN was 1.8%. There was no difference between age groups and sexes. CMN/CNLN were more frequent in children with a higher number of common melanocytic naevi (multivariate odds ratio, OR = 7.1 for the highest vs. the lowest quartile), consistent in small (OR = 7.2) and medium/large CMN/CNLN (OR = 6.0). Family history of malignant melanoma (OR = 1.4) and personal history of diabetes (OR = 4.4) appeared to be directly, and sun exposure inversely associated with CMN/CNLN. No relation was evident between CMN/CNLN and pigmentary traits, anthropometric characteristics, dietary habits, freckles, sunburns, sunscreen use or history of selected diseases. Conclusions: The association with family history of melanoma, the strong association with acquired melanocytic naevi, and the lack of association with pigmentary traits and sunburns suggest that CMN/CNLN may act as an independent risk marker for subjects at increased risk for cutaneous melanoma later in life.