[A rare melanocytic lesion occurring at birth, comprising at least 5% of the body surface area. It usually presents as a dark brown to black hairy lesion. Morphologically, it is characterized by the presence of a compound or intradermal nevus. There is an increased risk of malignant transformation to melanoma, rhabdomyosarcoma, and poorly differentiated malignant tumors. ( NCI )]
UMLS (NCI) C0334440