Abstract

Proliferative nodules (PNs) can irregularly occur on acquired and congenital melanocytic nevi (CMNs). As established over two decades ago, cases present in the immediate postnatal period as numerous small papules, nodules, or plaques, that can surround or occupy a giant congenital nevus. They are usually benign, rarely become malignant, and oftentimes regress. However, the risk of malignant melanoma increases with a large CMN, and emergence of a hyperpigmented or nodular area in a CMN mirrors malignant melanoma and indicates a prompt biopsy. Atypical features of PN on histology are not uncommon, complicating its distinction from melanoma. Herein, we present a PN in a CMN that occurred in a newborn male. This case demonstrates the significance of detailed histological interpretation for congenital lesions that cannot be grossly distinguished from malignant etiologies such as melanoma.

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