Acquired melanocytic nevi in childhood and familial melanoma.

IMPORTANCE In the surveillance of familial melanoma, the identification of children at greater risk of developing melanoma later in life would serve as a helpful tool. OBJECTIVE To determine whether acquired melanocytic nevi in childhood are an indicator of risk of melanoma in children from families with familial melanoma. DESIGN, SETTING, AND PARTICIPANTS A 20-year follow-up study of a cohort of children from families with familial melanoma. Phenotypical data on melanocytic nevi were collected from a random sample of 133 members of families with familial melanoma 2 to 18 years of age with variable risks of being a mutation carrier. More than 20 years of follow-up data (gene-carrier status, diagnosis of melanoma, and excisions of nevi) were collected. In a subgroup of 40 people, childhood phenotypical data were compared with data on nevus numbers in adulthood. Survival analyses, correlation analyses, and t tests were calculated to examine associations. MAIN OUTCOMES AND MEASURES Nevus count and distribution in childhood were correlated with the occurrence of melanoma and mutation carrier status. RESULTS Significant risk factors for melanoma were found, specifically in the group with the highest risk of being a mutation carrier: total number of atypical nevi in childhood (hazard ratio [HR], 1.21; 95% CI, 1.02-1.44; P = .03), the nevus count of atypical nevi on the buttocks (HR, 14.00; 95% CI, 2.94-66.55; P = .001), and the number of excisions during follow-up (HR, 1.27; 95% CI, 1.23-1.31; P < .001). The analysis also found a correlation between the distribution of nevi in childhood and adulthood and the distribution of melanomas (correlation, 0.89; 95% CI, 0.67-0.96; and correlation, 0.99; 95% CI, 0.98-1.00; P < .001, respectively for both). CONCLUSIONS AND RELEVANCE Numbers and distribution of melanocytic nevi in childhood are major indicators of the risk of melanoma in patients from families with familial melanoma.