Abstract
A case of thalamic primitive neuroectodermal tumor (PNET), metastasizing to the peritoneal cavity through the ventriculoperitoneal (V-P) shunt, is reported with special reference to the cytologic and immunocytologic findings of ascites cells. The patient was a 13 month-old male infant complaining of vomiting and disturbance of consciousness. CT revealed hydrocephalus and a cystic tumor, measuring 4cm in diameter, in the right thalamus. In spite of therapy including partial resection of the tumor, V-P shunt and Co irradiation, the patient died of cachexia with massive ascites 23 months later. At autopsy solid nodular tumors occupied the entire ventricles of the brain in association with necrotic and hemorrhagic foci, and in the peritoneal cavity, many nodular metastatic tumors in varying sizes showed similar characters. Histologically, both tumors consisted exclusively of rather small round undifferentiated cells. In the brain, small foci of spongioblastic, oligodendroblastic and ependymoblastic-type tumor cells were detected on occasion. Cytologically, the tumor cells were extremely undifferentiated, being closely similar to those of the small cell type of lung cancer. The immunocytologic results of ascites cells were the same as those observed in the tumor. Namely, antisera to S-100 protein, neurofilament and neuron specific enolase, except for glial fibrillary acidic protein, were positive in some tumor cells. These findings indicate that the PNET of our case originated from undifferentiated cells possessing multipotential ability to differentiate in the brain.
