A 3-month-old boy presented with a rapidly growing abdominal mass noticed by his mother since 1-week, with no other significant history.

On examination, the child had a large, firm, nontender mass extending from the left hypochondrium to the right. Lymphadenopathy or ascites was absent. Alpha-fetoprotein (AFP) was markedly elevated at 18,055 ng/mL (normal 0.2-9.0 ng/mL) with normal beta human chorionic gonadotropin level.

Contrast enhanced tomography of the abdomen and chest revealed a large retroperitoneal heterogeneous mass pushing the left kidney inferiorly and displacing the gut to the right [Figure 1].

|  Fig. 1 Axial contrast enhanced computed tomography of abdomen showing a large heterogeneous mass pushing the left kidney inferiorly and displacing the gut, no evidence of calcification

On exploration, a large intraperitoneal exophytic mass of size 8 cm × 9 cm × 8 cm was seen arising from the greater curvature and the posterior wall of the stomach occupying whole of the lesser sac [Figure 2]. It had variegated consistency with no involvement of adjacent structures and lymphadenopathy. The tumor was completely excised along with the involved gastric wall. Stomach was repaired in two layers.

|  Fig. 2 Intraoperative photograph demonstrating large mass arising from greater curvature and posterior wall of stomach

Histopathology revealed cystic, solid teratoid neoplasm, and a diagnosis of grade III immature teratoma was made. The tumor was seen invading the wall of the stomach and the resection margin of the stomach was free.

Postoperatively child remained healthy, and AFP levels came down to 5300 ng/mL. Child has been on regular follow-up for past 2 years with no recurrence.

|  Fig. 1 Axial contrast enhanced computed tomography of abdomen showing a large heterogeneous mass pushing the left kidney inferiorly and displacing the gut, no evidence of calcification