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.