Supplementary Material for: Gastric Adenocarcinoma with Enteroblastic Differentiation Resected through Endoscopic Submucosal Dissection: A Case Report

<b><i>Introduction:</i></b> Gastric adenocarcinoma with enteroblastic differentiation (GAED) is a rare histological type of gastric adenocarcinoma that occurs in the stomach and is known for its aggressive behavior. GAED is diagnosed histopathologically and is often advanced at the time of diagnosis. <b><i>Case Presentation:</i></b> We report the case of a 70-year-old male with a 20-mm superficial depressed lesion on the anterior wall of the antrum. Histological examination of the endoscopic submucosal dissection specimen revealed that the tumor was composed of dilated or slit-like branching tubules; additionally, the tumor cells had clear cytoplasm resembling that of the fetal digestive tract. Immunohistochemically, the tumor cells were positive for Glypican-3 and alpha-fetoprotein. A pathological diagnosis of GAEDs was established. GAED was found in approximately 30% of all the tumor cells and showed lymphatic invasion. The patient has been under recurrence-free follow-up for approximately 1 year after the endoscopic submucosal dissection. <b><i>Conclusion:</i></b> In order to detect a large number of cases, immunostaining should be aggressively performed if morphological findings are suspicious for GAED.