Metachronous Pineal Germinoma 11 Years After Total Resection of a Mature Teratoma

ABSTRACT

Central nervous system germ cell tumors are uncommon and include germinomas, teratomas, and other nongerminomatous germ cell tumors. Mature teratomas are usually cured by complete resection, but rare patients later develop a histologically distinct malignant germ cell tumor. We report a man who presented at age 20 years with a cystic pineal lesion. Gross‐total resection at age 21 years showed a mature teratoma with bronchogenic differentiation and no overt immature or malignant component on H&E. Serial postoperative MRI for 3 years showed no recurrence. Eleven years after surgery, he developed headache, gait disturbance, and confusion due to a 4.6‐cm pineal mass with obstructive hydrocephalus. Serum alpha‐fetoprotein was normal, whereas beta‐human chorionic gonadotropin (β‐hCG) was elevated. The resected tumor showed sheets of large round cells with clear cytoplasm and dense lymphocytes. Immunohistochemistry demonstrated strong nuclear OCT4 and SALL4 and membranous c‐KIT, with focal β‐hCG‐positive syncytiotrophoblastic giant cells. No nongerminomatous germ cell tumor component was identified, supporting a diagnosis of germinoma with focal syncytiotrophoblastic giant cells. After this diagnosis, retrospective evaluation of the initial tumor showed multifocal, patchy OCT4 immunoreactivity in scattered cells along the ciliated respiratory‐type epithelial lining. SALL4, c‐KIT, and PLAP were focally positive in corresponding regions. These findings raised the possibility of an occult germ cell marker‐positive population, although no discrete expansile germinoma component was identified. This case illustrates that metachronous germinoma can develop after a long disease‐free interval following resection of a mature teratoma and highlights the value of retrospective pathologic evaluation and long‐term surveillance.