Growing teratoma syndrome with extra pelvic metastasis and gliomatosis peritonei.

•Growing teratoma syndrome occurs when mature teratomas are discovered in patients who have previously received adjuvant chemotherapy for immature teratoma.•Gliomatosis peritonei is a rare condition often found alongside immature teratoma.•Synchronous identification of growing teratoma syndrome and gliomatosis peritonei has rarely been reported.•Comprehensive abdominopelvic imaging is critical to the surveillance protocol after treatment of immature teratoma to assess and appropriately treat this phenomenon.