Neonatal immature gastric teratoma: a case report.

Background: Gastric teratomas (GTs) are exceedingly rare neoplasms, accounting for less than 1% of all teratomas in children. Notably, GT arising from the anterior gastric wall is even rarer, with only a handful of cases reported in the literature, and the transmural growth pattern of such tumors further adds to their clinical uniqueness. Case presentation: We report a case of immature gastric teratoma arising from the anterior gastric wall in a term male neonate. The mass was detected on prenatal ultrasonography at 37 weeks and 6 days of gestation, and the infant was admitted on the first day of life for evaluation. Abdominal computed tomography revealed a heterogeneous mass measuring 51.9 mm × 47 mm × 39 mm in the hepatogastric space, containing calcifications and fatty components with close adhesion to the gastric wall; the transmural growth characteristic of the tumor was subsequently confirmed during surgical exploration. Laboratory studies demonstrated markedly elevated alpha-fetoprotein (AFP) (>60,500 ng/mL), neuron-specific enolase (NSE) (63.8 ng/mL), and lactate dehydrogenase (LDH) (575 U/L), which were suggestive of a germ cell tumor with comprehensive reference to clinical manifestations and imaging findings. The patient underwent complete surgical resection on postnatal day four. Histopathological examination confirmed a grade III immature teratoma with negative resection margins. Postoperative recovery was uneventful, with declining inflammatory markers at one-week follow-up. Conclusions: This case highlights the importance of including gastric teratoma in the differential diagnosis of neonatal abdominal masses, the diagnostic value of integrated imaging and tumor marker evaluation, and the necessity of complete surgical resection. Furthermore, it demonstrates the critical role of multidisciplinary collaboration in the timely diagnosis and management of rare neonatal tumors.