Mondo Description A large, or giant, congenital melanocytic nevus (LCMN or GCMN) is a pigmented skin lesion of more than 20 cm - or 40 cm- respectively, projected adult diameter, composed of melanocytes, and presenting with an elevated risk of malignant transformation.

Uniprot Description A syndrome characterized by congenital pigmentary skin lesions which can occur at any site and can cover most of the body surface. These lesions may or may not be hairy. Congenital melanocytic nevi are associated with neuromelanosis (the presence of melanin-producing cells within the brain parenchyma or leptomeninges). Less commonly they are associated with malignant melanoma in childhood, both in the skin and the central nervous system. CMNS patients also tend to have a characteristic facial appearance, including wide or prominent forehead, periorbital fullness, small short nose with narrow nasal bridge, round face, full cheeks, prominent premaxilla, and everted lower lip.