obsolete spitz nevus true OBSOLETE. 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. MONDO:0007658 Obsoleted as was conflated with congenital melanocytic nevus spitz nevus