Abstract
We report the first case of early gastric cancer just above a heterotopic pancreas for which the differential diagnosis was carcinoma arising from heterotopic pancreas. Routine upper gastrointestinal endoscopy in an 83-year-old man with sigmoid colon cancer revealed a gastric cancer in the lesser curvature of the antrum. Endoscopic ultrasonography (EUS) for evaluating the depth of tumor invasion revealed a hypoechoic mass in the submucosal layer. The depth of tumor invasion was diagnosed as muscularis propria. Distal gastrectomy and sigmoidectomy were performed. Histologically, the resected specimen of the stomach unexpectedly revealed a heterotopic pancreas just below the gastric cancer. They were not linked, and the heterotopic pancreas had no dysplasia. The gastric cancer had slightly invaded the submucosa. The hypoechoic mass on EUS was not the invasive tumor but the heterotopic pancreas. The preoperative staging of the gastric cancer on EUS was confounded by the presence of the heterotopic pancreas just below the gastric cancer.