Abstract
Pigmented lesions in a 21-day-old boy with congenital giant pigmented nevus were studied light and electron microscopically. There were nests of nevus cells in the upper, and neurofibromatous structure in the middle and lower portions of the dermis. One of specimens, obtained from a pigmented nodule with a central keratotic mass, showed hyaline cartilage and bundles of smooth muscle cells in addition to nevus cells and neurofibromatous tissue. One of the chondrocytes was found to have a melanosome complex. In general, it is considered that the neural crest contributes to the formation of a pigmentary system, nervous system as well as skeletal and connective tissue. Cells of the neural crest which form bone, cartilage, connective tissue and smooth muscle in the cephalic region have been called “mesectoderm”. Thus, it is speculated that the cells which composed giant pigmented nevus in our patient, are all derived from the neural crest and/or mesectoderm. Neural crest underdevelopment seems to account for the giant pigmented nevus.
