A 70s man admitted to our hospital with a gastric abnormality. Esophagogastroduodenoscopy showed submucosal tumor-like lesion, approximately 25 mm in diameter, on lesser curvature of middle corpus of the stomach and depressed lesion on the top of the elevation. Biopsy specimens indicated well-differentiated tubular adenocarcinoma. Endoscopic ultrasonography (EUS) revealed multiple heterotopic gastric glands mainly in the gastric submucosa, which were diagnosed diffuse cystic malformation (DCM). We performed endoscopic submucosal dissection (ESD) for early gastric cancer based on DCM. DCM frequently causes gastric cancer, but DCM makes it difficult to diagnose the invasion depth by conventional endoscopy. Consequently EUS is important in deciding the treatment strategy for gastric cancer with DCM. Careful follow-up observation is necessary in consideration of the occurrence of metachronous gastric cancer because cancer often occurs frequently.
