Giant Congenital Melanocytic Nevi

Abstract

Giant or large congenital melanocytic nevi (CMNs) measuring more than 20 cm in diameter are present in 1 out of 20 000 newborns, with an estimated 6.3% lifetime risk of developing malignant melanoma. Approximately half of all melanomas that arise within a giant congenital nevus do so by 5 years of age. They occur most commonly on the posterior trunk but may also appear on the head or the extremities. Congenital pigmented nevi have been categorized by size: Giant congenital nevi are more than 20 cm in diameter; small congenital nevi are less than 2 cm in diameter; and intermediate nevi are in between in size. Giant nevi frequently lie in the distribution of a dermatome and will cover areas like an arm, leg, or a significant part of the trunk. These lesions are usually termed in a descriptive manner, for example, coat-sleeve, stocking, bathing-trunk, or giant hairy nevi. Giant hairy nevi are associated with neurological disorders. Nevi on the scalp and neck are associated with an increased incidence of leptomeningeal melanocytosis, epilepsy, and other focal neurological abnormalities. Those located over the vertebral column are associated with increased risk of spina bifida and meningomyelocele. The presence of ‘‘satellite’’ melanocytic nevi increases the risk of leptomeningeal involvement, particularly when located on the head or midline on the trunk. Nevus cells within the leptomeninges may cause increased intracranial pressure with subsequent hydrocephalus, seizures, and motor deficits. We describe a newborn with a bathing-trunk giant congenital pigmented nevus. Case Report