Large Congenital Melanocytic Nevi and the Risk for the Development of Malignant Melanoma

Abstract

Patients with large congenital melanocytic nevi have been described to have an increased risk for the development of malignant melanoma (MM). Ninety-two patients with large congenital melanocytic nevi were followed up prospectively for the development of MM. Matched individuals from the general population served as control subjects. Ninety-two patients (median age, 3 years) were followed up prospectively for an average of 5.4 years. In three patients (3%), MM developed in extracutaneous sites. The cumulative 5-year life-table risk for the development of MM was calculated to be 4.5% (95% confidence interval, 0% to 9.3%). In individuals in the general US population, matched for age, sex, and length of follow-up to the 92 study patients, 0.013 would be expected to develop MM. The standardized morbidity ratio (adjusted relative risk) was calculated to be 239, which was highly significant (P < .001). Patients with large congenital melanocytic nevi are at a significantly increased risk for the development of MM and should be kept under continuous surveillance for the development of cutaneous as well as noncutaneous primary MM.