Neonatal giant congenital nevi with proliferative nodules: a clinicopathologic study and literature review of neonatal melanoma.

BACKGROUND Review of the literature reveals that congenital malignant melanoma is an exceptionally rare occurrence and has a generally poor prognosis when it does occur. However, benign proliferative melanocytic lesions are known to occur within giant congenital nevi (GCN). This entity is not well recognized and can be confused clinically and histologically with malignant change. OBSERVATIONS We report 2 cases of GCN in neonates demonstrating benign proliferating nodules present at birth. An initial diagnosis of malignant melanoma was assumed in both cases. Careful histologic analysis, however, revealed these lesions to be benign, as did long-term follow-up of 3.5 years, with both patients remaining well with no evidence of melanoma. Review of the literature suggests that there are 2 clinical patterns of these benign nodules arising within GCNs: small (<1 cm) and large (>1 cm) dermal nodules with varying histologic patterns that we have attempted to categorize. CONCLUSIONS Our cases illustrate the difficulty in accurate diagnosis of melanocytic lesions in the neonate. We recommend caution in making a diagnosis of malignant melanoma and highlight the possibility that benign lesions can be mistaken for melanoma in this age group. We encourage the acquisition of fixed histologic specimens for accurate diagnosis of melanocytic lesions.