Mature Gastric Teratoma in a 3-Month-Old Male Infant Presenting With Progressive Abdominal Distension: A Rare Pediatric Tumor With Complex Diagnostic and Surgical Considerations.

Gastric teratoma is a sporadic pediatric tumor, usually appearing in early infancy. We present a 3-month-old male infant with progressive abdominal distension, chronic constipation, and a firm upper-abdominal mass. Imaging showed a large heterogeneous lesion originating from the greater curvature of the stomach, with mixed solid and cystic components suggestive of a teratoma. The mass was entirely removed via laparotomy, and histopathology confirmed a mature gastric teratoma containing tissues from all three germ layers without malignant features. The postoperative recovery was smooth, with rapid symptom improvement. This case emphasizes the importance of considering gastric teratoma in infants with unexplained abdominal distension and supports complete surgical removal as an effective management approach in this case.