Considering that MUC5AC and MUC6 are usually expressed in the gastric foveolar epithelium and the pyloric gland of the stomach, respectively, whereas MUC2 and CD10 are usually expressed in the small intestinal epithelium, we suspect that our patient's adenocarcinoma developed from the ectopic gastric mucosa of the MD. The gene discussed is MUC2; the disease is adenocarcinoma.