Endscopic Submucosal Dissection of a Heterotopic Gastric Mucosa in the Stomach: Report of a Case

A 38-year-old man with a submucosal tumor (SMT) at the anterior wall of the pylorus underwent upper gastrointestinal endoscopy. The tumor was 40 mm in diameter with a long stalk extending into the duodenal bulb. In addition, the long stalk had an ulcer with a blood vessel. Removal of this tumor was initially considered to be possible only by distal gastrectomy. However, endoscopic ultrasound (EUS) was subsequently proven to be a reliable investigative procedure for evaluating the lesion. The tumor was characterized by its origin in the second layer, and endoscopic submucosal dissection (ESD) was performed. En bloc resection of a 32 × 20 × 40 mm area of tissue with tumor-free lateral/vertical margins was accomplished without complication. Histopathological examination confirmed a heterotopic gastric mucosa. By immunostaining, the neoplasm was positive for MUC6 and negative for amylase and trypsin. In this case, EUS was used to investigate a heterotopic gastric mucosa that originated in the second layer, with no infiltration of the fourth layer under the tumor. Therefore, we performed successful ESD at the appropriate layer