Congenital melanocytic nevi and risk of melanoma.

The presence of congenital melanocytic nevi (CMN) is determined in utero. The location, size, and number of CMN may be of cosmetic concern with significant psychosocial implications. They may also be associated with symptoms such as pruritus, eczema/xerosis, and skin fragilit; however, the most medically concerning issue is the association of CMN with the risk of developing cutaneous melanoma, extracutaneous melanoma, and neurocutaneous melanocytosis (NCM). Patients with CMN are currently risk-stratified based on the projected adult maximum diameter of the largest CMN and the number of CMN (satellites) present. In small and medium CMN the absolute risk of developing cutaneous melanoma is estimated to be approximately 0.3% with a relative risk of 9.5. While patients with large CMN are at increased risk for developing primary cutaneous melanoma within the CMN, they are also at increased risk for developing primary melanoma within the central nervous system (CNS) in association with CNS melanocytic deposits, an entity known as NCM. The absolute risk for developing melanoma in patients with large CMN is estimated to be between 1.25-10% with a relative risk between 52-1046. Regarding the risk for the presence of NCM, the risk correlates with the number of CMN, with the lowest risk in those with a single CMN and with risk escalation as the number of CMN increase. We have provided an overview of the existing evidence about the risk of melanoma and NCM in patients with CMN. The role of the clinical examination, dermatoscopy, MRI scanning of the CNS, and the role of surgery in the management of CMN of varying sizes is discussed.