Primary germinoma arising from the midbrain.

A 29-year-old man presented with diplopia, dysarthria, anisocoria, oculomotor nerve paralysis, abducens nerve paralysis, right facial palsy, and spastic hemiparetic gait. Magnetic resonance imaging (MRI) showed a homogenously enhanced mass in the midbrain. MRI-guided stereotactic biopsy was performed, and the histologic diagnosis was pure germinoma. The tumor disappeared after chemotherapy and radiotherapy. Germinoma should be included in the differential diagnosis of midbrain lesions in young adults. MRI-guided stereotactic biopsy provided a helpful diagnostic clue in a patient with a midbrain lesion.