Germ cell tumors (germinoma and yolk sac tumor) in unusual sites in the brain.

This report presents three cases of primary intracranial germ cell tumor encountered in unusual sites, or essentially non-midline structures. The three provided the opportunity to examine surgically obtained tissues with the electron microscope. The histological diagnosis was initially made by light microscopic observations. The first case was a 10-year-old boy in whom the tumor occupied the right thalamic and basal ganglionic region and was diagnosed as a yolk sac tumor. The second an 11-year-old boy who presented with a mass lesion on the left thalamic and basal ganglionic region, diagnosed as germinoma. The third was a 39-year-old man who presented with multiple tumors in the ventricular system and posterior fossa, also diagnosed as germinoma. Among the three cases, neither diabetes insipidus nor ophthalmologic disorder was manifested. Extensive examination and autopsy findings indicated that these intracranial lesions had not metastasized from primary extracranial tumors, including those of the genital organs.