[Primitive neuroectodermal tumor with peritoneal metastasis through a ventriculoperitoneal shunt. Case report].

A 13-month-old boy admitted with lethargy and hydrocephalus was found to have a right thalamic mass. Ventricular drainage was instituted, and the tumor mass was reduced by partial resection and local irradiation. A ventriculoperitoneal shunt was then placed. However, the tumor recurred 16 months later, with extensive ventricular seeding and peritoneal metastasis through the shunt tube. The child died 22 months after onset. Histological study of surgical specimens of the primary tumor and autopsy specimens of the brain and peritoneal metastatic tumors revealed poorly differentiated, small, round cells with numerous mitotic figures. In addition, autopsy specimens of the brain tumor contained areas of ependymal, oligodendroblastic, and spongioblastic differentiation. On immunohistochemical study, the tumor cells of each specimen were positive for anti-neuron specific enolase and anti-neurofilament antibodies, but negative for anti-glial fibrillary acidic protein antibodies. Electron microscopy revealed some zonulae adherens. These findings strongly suggest that the tumor originated from primitive multipotential cells capable of differentiating into ependymal, glial, and neuronal lines.