Melanoma risk in congenital melanocytic naevi: a systematic review

BACKGROUND: The risk of malignant melanoma in congenital melanocytic naevi (CMN) is a matter of controversial and ongoing debate. OBJECTIVES: The purpose of this systematic review is to provide a careful and detailed summary of the published data, including several recently published studies. METHODS: Articles on CMN (n=1424) were retrieved from Medline, 1966-October 2005. Case reports and studies lacking relevant clinical information were excluded. Only systematic collections of cases were taken into consideration. Series with fewer than 20 patients or studies with a mean follow-up of or=40 cm in diameter. CONCLUSIONS: The overall risk of melanoma of 0.7% in all 14 studies was lower than expected. The higher incidence of melanomas in smaller studies indicates selection bias. The melanoma risk strongly depends on the size of CMN and is highest in those naevi traditionally designated as garment naevi. The median age of 7 years at diagnosis of melanoma points to a risk maximum in childhood and adolescence. Future studies on CMN should report: (i) diameter, percentage of body surface, and localization of the CMN; (ii) percentage of naevus area removed by excision or subject to dermabrasion or other superficial treatments; (iii) mean and median age at entry into the study; (iv) mean and median follow-up time; (v) details on each melanoma case; (vi) standardized morbidity ratio of melanoma; and (vii) percentage of neurocutaneous melanosis.