Objective To study the clinicopathologic features, pathogenesis and differential diagnosis of Neurocutaneous Melanosis(NCM).Methods The clinic and pathologic features in 1 case of NCM was analyzed.Immunohistochemical study were performed.Results A 21-year-old woman with a history of giant congenital nevus at birth and Dandy-Walker syndrome.MRI demonstrates extensive leptomeningeal enhancement and a cyst in the posterior fossa.Under microscope, melanocytes with variable pigmentation, cells positive for HMB45,MelanA,S-100,S -100、 Vimentin, negetive for GFAP, NF.ki-67 positive cell<1%.Conclusions NCM is a rare phakomatosis characterized by a focal or diffuse proliferation of melanin-producing cells in both the skin and the leptomeninges.NCM is considered to follow from neurulation disorders which could account for Dandy-Walker complex.Definite diagnosis relies upon the histological data obtained by mean of biopsy.Once symptomatic, surgical and medical measuresremain palliative since death occurs usually within 3 years.