Congenital melanocytic nevi.

This article reviews congenital melanocytic nevi (CMN), which are present at birth or appear shortly thereafter, and their main histologic features. Several histologic variants and histopathologic criteria that differentiate CMN from other nevi, such as atypical or dysplastic nevi, and from nevoid malignant melanoma, are discussed. Histologic pitfalls in the correct identification of lentiginous melanocytic hyperplasia, pagetoid scatter, and proliferative nodules in the context of CMN are discussed. The risk for development of malignant melanoma in association with a congenital melanocytic nevus and variable causes for changing mole are discussed.