Pituitary germinoma after resection of a mature third ventricular teratoma: illustrative case

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BACKGROUND Metachronous intracranial germ cell tumors (iGCTs)—unrelated, histologically different iGCTs occurring at different time points—occurring within the same patient remain a rarity. Herein, the authors report such a case and discuss the literature and potential pathophysiological mechanisms leading to this phenomenon. OBSERVATIONS A 9-year-old boy presented with new-onset impaired balance, headaches, nausea, visual disturbances, and left facial paresis. Magnetic resonance imaging (MRI) scans revealed a suspected pineal region teratoma originating from the pineal gland with consecutive obstructive hydrocephalus. A mature teratoma was diagnosed and resected. Postoperative recovery was good, and the patient could return to his normal daily activities. However, a new, slowly progressive lesion in the sellar region with an enlarged infundibular stalk was detected on follow-up MRI 3.5 years after initial pineal region teratoma resection. Biopsy revealed a newly developed pure germinoma. The patient was treated with radiotherapy plus chemotherapy and remained relapse free at the last follow-up. Sixteen other cases have reported a surgically resected primary mature teratoma, wherein patients developed metachronous germinomas during follow-up. Different theories try to elaborate this phenomenon, yet none can completely account for it. LESSONS Although rare, metachronous iGCT is a phenomenon neurosurgeons should be aware of. In patients treated for iGCT, close long-term clinical, imaging, and laboratory follow-up is recommended. https://thejns.org/doi/10.3171/CASE2443