Thalamo-peduncular germinoma in a young adult: a case report.

Germinomas arising in deep brain structures such as the thalamus and cerebral peduncles are rare and frequently mimic high-grade gliomas, creating diagnostic uncertainty. We report the case of a 23-year-old man presenting with progressive headaches, visual disturbances, and signs of intracranial hypertension with secondary hemiparesis and speech impairment. Brain magnetic resonance imaging (MRI) showed a thalamo-peduncular mass suggestive of infiltrative glioma. Stereotactic biopsy with immunohistochemistry demonstrated strong CD117, PLAP, and OCT4 expression, confirming a pure germinoma. Staging revealed pulmonary micronodules and para-aortic lymphadenopathy, while serum tumor markers were normal. The patient was treated with platinum-based chemotherapy followed by craniospinal radiotherapy, with marked clinical improvement and radiological stability. This case illustrates the diagnostic challenge of deep midline germinomas and emphasizes the essential role of histological confirmation to ensure appropriate, potentially curative treatment.