ROLE OF POSITRON EMISSION TOMOGRAPHY IN THE MANAGEMENT OF NEUROCUTANEOUS MELANOCYTOSIS Abstract: Management of large congenital melan- ocytic nevi and neurocutaneous melanocytosis repre- sents a difficult challenge for clinicians, due to the high risk of malignancy in both entities and the difficulty of an early diagnosis of this complication. We report a new case of neurocutaneous melanocytosis (NCM) in asso- ciation with large congenital melanocytic nevi (LCMN) that illustrates a possible role of positron emission tomography in the work-up of these patients. Neurocutaneous melanocytosis (NCM) is a rare dis- order associated with large congenital melanocytic nevi (LCMN). It is thought to represent an embryonal neuroectodermal dysplasia with excessive proliferation of melanocytes. During a 10-year period, we have been following in our clinic a case of LCMN involving the trunk and upper legs of a young boy, with a great number of atypical satellite nevi (Figs. 1 and 2). When he was 3- years-old, he presented with neurologic involvement with motor deficits in both legs and left arm, seizures, and development delay. Magnetic resonance imaging (MRI) with T1-weighted noncontrast images showed mixed signal in the pons (peripheral hyperintensity due to melanin and central hypointensity probably due to calcification areas), cisterna magna enlargement and hypoplasia of the cerebellar hemisphere and brain stem. The child was diagnosed with NCM. During the follow-up period, after a long period of being asymptomatic, the child presented with a seizure, and malignant transformation of NCM to melanoma was considered. To rule out malignant degeneration, po- sitron emission tomography (PET) with 18-FDG of the whole body including the central nervous systems (CNS) was performed. No pathologic deposits of the radionuclide were seen in the CNS or whole body PET scans (Fig. 3), interpreted as consistent with the benign clinical evolution of the disease to date in our patient. Neurocutaneous melanocytosis (NCM) is charac- terized by the presence of benign and ⁄ or malignant melanocytic proliferations in the CNS in association with LCMN or 3 or more smaller congenital mel- anocytic nevi (1). Magnetic resonance imaging (MRI) with contrast is the best diagnostic imaging modality for diagnosing NCM. T1-weighted shortening in a MRI scan suggests the presence of melanin in the CNS (2). 18F-FDG positron emission tomography is the principal staging technique for the assessment of meta- static and recurrent melanoma, used in conjunction with Figure 1. Large congenital hairy melanocytic nevi involving both thighs and abdomen, with many satellite nevi. Figure 2. Dorsal image of large congenital melanocytic nevi, involving almost completely the back. Figure 3. CNS 18F-FDG positron emission tomography with a slight global hypometabolism but no pathologic depo- sition. Brief Reports 351