A prospective study of patients with large congenital melanocytic nevi and the risk of melanoma

Background: large congenital melanocytic nevus (lcmn) is considered a risk factor for melanoma,although the magnitude of this risk is controversial. objective: to evaluate the risk of melanoma development in patients with lcmn seen at a dermatology referral center in brazil during a twelve-year period. to the best of our knowledge,there are no published similar studies on large congenital melanocytic nevus in south america. methods: our prospective cohort included only patients with congenital nevi ≥20cm. the cumulative risk of developing melanoma and the standardized morbidity ratio were calculated for patients followed up prospectively for at least 1 month. results: sixty-three patients were enrolled in this study. one patient who developed melanoma prior to enrollment was excluded,and five were eliminated because of insufficient follow-up time. mean follow-up for the remaining 57 patients was 5.5 years (median 5.2 years). median age of entry into the study was 2.6 years. most patients (75.4%) underwent only clinical observation. melanomas occurred in 2 (3.5%) patients. five-year cumulative risk for melanoma was 4.8% (95% ci: 1.9-11.5%). standardized morbidity ratio was 1584 (95% ci: 266-5232,p<0.001). study limitations: the small sample size reduces the accuracy of risk estimates. conclusions: this study analyzed prospectively for the first time data from south america demonstrating that patients with lcmn have a higher risk of developing melanoma than the general population (p<0.001). © 2017 by anais brasileiros de dermatologia.