Yolk sac tumor in the fourth ventricle: a case report.

The nongerminomatous germ cell tumor occurring in the fourth ventricle is extremely rare. A 9-year-old boy presented with symptoms of obvious headache, projectile vomiting, diplopia and motor weakness. MRI scanning revealed lesions occupying the fourth ventricle, with dual-lateral ventricle expansion after gadolinium administration. Suboccipital craniectomy was performed and the tumor was removed by block resection. Twice intraoperative biopsy specimens revealed fiber vascular tissue and hemangioma. Histological examination revealed that the tumor consisted of loose network structures and Schiller-Duval bodies. Immunohistochemical study showed that the primitive germ cells were positive for placental alkaline phosphatase, alpha-fetoprotein, cytokeratin, vimentin, but negative for glial fibrillary acidic protein. The histological diagnosis was pure yolk sac tumor. Two years after surgery, he has suffered no tumor recurrence. A combination of surgical treatment, radiation and chemotherapy is mandatory.