Yolk sac tumor of unknown origin with intracranial and spinal metastases.

Primary intracranial yolk sac tumor (Endodermal sinus tumor, YST) is quite rare, and most usually involves the pineal gland. This report concerns a rare case of unknown origin of yolk sac tumor with intracranial and spinal metastases. The 6-year-old boy initially manifested symptoms of acute urinary retension and paraparesis. Computed tomography (CT) and magnetic resonance imaging (MRI) revealed an intrathecal tumor spreading below the third lumbar segment, and tumors also appeared in the left temporal area and right cerebellar hemisphere. The pineal region was free of neoplastic involvement and the gonads were normal. The patients underwent operation to remove intracranial and spinal tumors, and postoperative radiotherapy was administered. The histological findings showed metastatic yolk sac tumor. Multiple intracranial and spinal seeding were noticed postoperatively. The patient died of recurrent YST and pneumonia three months after operation. The origin of secondary YST can always be found in specific midline sites. This is a rare case since the primary lesion is unknown.