High-Grade Immature Gastric Teratoma in a 10-Day-Old Neonate: Diagnostic Challenges and Curative Surgical Management.

Neonatal gastric teratomas are exceptionally rare germ cell tumors (<1% of pediatric teratomas) posing significant diagnostic and surgical challenges. Immature variants, particularly high‑grade tumors, can be locally aggressive yet typically have a favorable prognosis if completely resected. We report a 10‑day‑old male neonate (born at 36+1 weeks to a mother with gestational diabetes and pregnancy‑induced hypertension) presenting with a firm epigastric and left hypochondriac mass detected 24 hours after birth. Imaging revealed a mixed echogenic lesion containing fat and calcifications from the stomach's lesser curvature, and serum alpha‑fetoprotein was markedly elevated for age. On day 12, an exploratory laparotomy achieved en bloc resection via partial gastrectomy with clear margins, despite dense adhesions to the left hepatic lobe and an intragastric component. Postoperatively, the patient experienced a right femoral artery thrombosis managed with anticoagulation and wound dehiscence addressed by local care and antibiotics. Histopathology confirmed a Grade III immature gastric teratoma without malignant germ cell elements; a splenule was also identified. An upper gastrointestinal contrast study on postoperative day 11 showed an intact repair, and feeds were successfully advanced. This case underscores the importance of suspecting gastric teratoma in neonates, interpreting age‑adjusted tumor markers carefully, and ensuring complete surgical excision. Vigilant perioperative management and long‑term surveillance with serial imaging and alpha‑fetoprotein monitoring remain paramount, particularly for high‑grade immature lesions.