Yolk sac tumor of the bilateral basal ganglia in a patient with Down syndrome.

We report a case of intracranial yolk sac tumor in a 17-year-old girl with Down syndrome who presented with left slowly progressive hemiparesis. Initial magnetic resonance imaging (MRI) showed a small area of ill-defined abnormal signal intensity without a mass in the bilateral basal ganglia. These findings progressed very slowly for 2 years, but then the lesion rapidly progressed to a huge mass on MRI 4 months after the previous scan. The patient subsequently underwent a blood examination and endoscopic biopsy, and was finally diagnosed with yolk sac tumor. Standard platinum-based chemotherapy and radiotherapy were performed as soon as practicable. The frequency of solid cancer in patients with Down syndrome is generally lower than that in individuals without this disorder. Brain tumor is also rare in Down syndrome, but half of these cases are germ cell tumors. Moreover, slowly progressive non-tumor-like lesions in the basal ganglia may also be germ cell tumors. Therefore, MRI signal abnormalities in the basal ganglia in patients with Down syndrome require careful and frequent follow-up scans based on the possibility of a germ cell tumor that may exhibit rapid growth.