Large congenital melanocytic nevi

Abstract

B large congenital melanocytic nevus (LCMN), defined herein as a nevus present at birth that is predicted to be at least 20 cm in greatest diameter in adulthood, occurs infrequently. Approximately one in 20,000 infants, amounting to 200 newborns per year in the United States, is born with a LCMN. In addition, one in 500,000 newborns, translating to 10 infants, is born each year with very large LCMN of the garment or bathing-trunks type. 1 The implications for the affected infant are significant. Beside cosmetic disfigurement, a LCMN increases an individual's risk for developing malignant melanoma (MM), and may be associated with neurocutaneous melanocytosis (NCM). 25 There are many definitions for what constitutes a LCMN (Table 1). 6-13 As mentioned above, we elect to define LCMN based on the predicted maximum diameter of the nevus in adulthood: at least 20 cm. Congenital melanocytic nevi (CMN) generally enlarge in proportion to the growth of the skin coveting the involved area of the body. 14 Figure 1 depicts the graphs we use to predict the adult diameter of an infant's or child's CMN. 15 Clinically, LCMN can be light brown, dark brown, black, blue, or exhibit a combination of colors. The surface may be macular, papular, mamillated, hyperkeratotic, rugose, and/or nodular. The nevus may be hypertrichotic. 16 With time, LCMN may get darker or lighter, and rarely, completely disappear.5,! 6,17 LCMN can sometimes be associated with anomalies such as NCM, neurofibromatosis type I, occult spinal dysraphism, and/or the tethered cord syndromeJ 8 NCM may affect over 10% of patients with LCMN. 15 It is a s2cndrome with a poor prognosis for survival. According to one definition, NCM is characterized by the presence of an LCMN, or multiple (three or more) smallto medium-size CMN, accompanied by a benign and/or malignant melanocytic proliferation in the leptomeningesJ 9 Of the patients with central ner-