large congenital melanocytic nevus (MONDO_0044792) is 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. Also known as: GMN, Giant Congenital Melanocytic Nevus, LCMN, bathing trunk nevus, congenital melanocytic nevi, congenital melanocytic nevus, congenital melanocytic nevus of skin, congenital melanocytic nevus of the skin.