Pathological findings showed gastric cancer (papillary adenocarcinoma and moderately differentiated tubular adenocarcinoma) positive for mucin 5AC (MUC5AC), and duodenal cancer (solid-type poorly differentiated adenocarcinoma > non-solid-type poorly differentiated adenocarcinoma) positive for MUC5AC and mucin 6 (MUC6), with both tumors meeting at the pyloric ring. This evidence concerns the gene MUC6 and gastric cancer.