We report a rare case of gastric adenocarcinoma with enteroblastic differentiation (GAED) that was treated with endoscopic submucosal dissection followed by additional distal gastrectomy with lymph node dissection. A 67-year-old man underwent endoscopic submucosal dissection for a gastric lesion, which was diagnosed as GAED with submucosal and lymphatic invasion. Histologically, GAED is characterized by a tubulopapillary growth pattern and clear cells that resemble those of the primitive fetal gut. Immunohistochemically, GAED variably expresses oncofetal proteins such as glypican-3, alpha-fetoprotein, and spalt-like transcription factor 4. Despite negative margins, additional gastrectomy with lymph node dissection was performed due to submucosal and lymphatic invasion. No residual tumor or metastasis was detected, and the patient remained disease-free for 2 years before dying from causes unrelated to GAED. Given its aggressive nature, frequent lymphovascular invasion, and high metastatic potential, clinicians should recognize the histopathological diagnosis of this rare tumor and its propensity for aggressiveness.

Subepithelial tumors in the upper gastrointestinal (GI) tract are often detected during nationwide endoscopic gastric cancer screening in Korea. Most GI lipomas are asymptomatic and do not necessitate further treatment. However, large tumors may lead to complications such as bowel obstruction, intussusception, and bleeding. These GI lipomas require endoscopic or surgical resection. On radiological examination, GI lipomas typically manifest as hypodense lesions with similar density to that of fat tissue. White-light endoscopy generally reveals a yellowish subepithelial tumor exhibiting a positive cushion sign, while endoscopic ultrasonography shows a homogeneous hypoechoic mass within the third layer of the GI tract. We present the case of an 81-year-old woman with symptomatic duodenal lipoma following endoscopic resection.