异时性颅内生殖细胞肿瘤（iGCT）与不同时间点发生的无关、组织学上不同的 iGCT 发生在同一患者体内仍然很少见。在此，作者报告了这样一个病例，并讨论了文献和导致这种现象的潜在病理生理机制。 一名 9 岁男孩出现新发平衡障碍、头痛、恶心、视力障碍和左侧面神经麻痹。磁共振成像（MRI）扫描显示疑似松果体区畸胎瘤源自松果体，并伴有连续阻塞性脑积水。诊断出成熟畸胎瘤并予以切除。术后恢复良好，患者可以恢复正常的日常生活。然而，在初次松果体区畸胎瘤切除术后 3.5 年，随访 MRI 检测到鞍区出现新的、缓慢进展的病变，并伴有漏斗柄增大。活组织检查显示出新发展的纯生殖细胞瘤。该患者接受了放疗加化疗，并在最后一次随访时保持无复发。其他 16 例报告了手术切除的原发性成熟畸胎瘤，其中患者在随访期间出现异时性生殖细胞瘤。不同的理论试图阐述这一现象，但没有一个能够完全解释它。尽管异时性 iGCT 很罕见，但神经外科医生应该意识到这种现象。对于接受 iGCT 治疗的患者，建议进行密切的长期临床、影像学和实验室随访。 https://thejns.org/doi/10.3171/CASE2443。

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.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.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.