Peritoneal implantation of endodermal sinus tumor of the pineal region via a ventriculoperitoneal shunt. Cytodiagnosis with immunocytochemical demonstration of alpha-fetoprotein.

A 17-year-old male developed an endodermal sinus tumor in the pineal region that metastasized to the peritoneal cavity via a ventriculoperitoneal shunt and caused ascites. Neoplasm was diagnosed by cytologic examination of the peritoneal fluid, and the precise histologic nature of the neoplasm was confirmed by immunocytochemistry, which demonstrated alpha-fetoprotein in the neoplastic cells.