Neurocutaneous melanosis with the Dandy-Walker malformation: one case report

Objective To investigate the clinic and pathologic features of one patient diagnosed with neurocutaneous melanosis (NCM) by biopsy. Methods A 21-year-old woman presented with a 2-month history of tinnitus, headache, vomiting and 1-month history of impaired vision. At birth, a massive nevus covering most of the posterior abdomen had been noted as well as the presence of multiple smaller lesions all over the body. Magnetic resonance imaging demonstrated a posterior fossa cyst compatible with the Dandy-Walker syndrome and extensive leptomeningeal enhancement. Surgery was performed to cystectomy and to obtain pathologic specimens from the leptomeninges. Biopsy and immunohistochemical study was performed. Results At surgery, diffuse black pigmentation of the leptomeninges and the cyst was found. Under microscope, the cyst and leptomeninges were composed with melanocytes with variable pigmentation. Those cells positive for HMB45, MelanA, S100 and vimentin. Ki-67 positive cells<1%. The pathologic diagnosis was leptomeningeal diffuse melanocytosis. The patient died 2 months after the surgery. Conclusions NCM is characterized by a focal or diffuse proliferation of melanin-producing cells in both the skin and the leptomeninges. NCM could be compatible with the Dandy-Walker syndrome. Definite diagnosis relies upon the histological data obtained by mean of biopsy. Key words: Melanosis; Neurocutaneous syndromes; Dandy-walker syndrome