Unusual anatomic location of a primary intracranial yolk sac tumor.

A nongerminomatous germ cell tumor occurring in the brain parenchyma is extremely rare. A 2-year-old boy presented with symptoms of abnormal movements in the hand and mouth. MRI scanning revealed a lesion occupying the left temporoparietal region. Craniotomy was performed and the tumor was removed by en bloc resection. Histological examination revealed that the tumor was arranged in a reticular pattern, and Schiller-Duval bodies were evident at the center of the tumor. Immunohistochemical study showed that the tumor cells were positive for alpha-fetoprotein and vimentin, but negative for glial fibrillary acidic protein. The histological diagnosis was pure yolk sac tumor.