Bilateral germ cell tumors involving the basal ganglia and thalamus.

Two cases of a human chorionic gonadotropin-producing germ cell tumor originating bilaterally in the basal ganglia and thalamus are reported. The biological behavior and clinical characteristics were similar to those of unilateral germinomas involving the basal ganglia and thalamus. Common clinical features were slowly progressive unilateral pyramidal signs and bilateral and/or unilateral extrapyramidal signs which occurred either concomitantly or sequentially. Bilateral symmetrical lesions were demonstrated by computed tomography and/or magnetic resonance imaging at an early stage of illness. Serum and cerebrospinal fluid human chorionic gonadotropin levels were elevated (116 and 141 mIU/ml, respectively) but decreased and remained within normal limits after radiation therapy alone. Radiosensitivity was confirmed by repeated computed tomographic scans and tumor marker measurements. Multiple concomitant germ cell tumors is a rare, but interesting lesion, especially considering its pathogenesis and oncogenesis.