A Japanese man was being followed after he underwent left hepatectomy and pancreatoduodenectomy for a mucin-producing hilar cholangiocarcinoma (the postoperative pathological diagnosis was well differentiated papillary adenocarcinoma, T2, N0, M0, stage II by the International Union Against Cancer TNM classification) and lower bile duct carcinoma (the postoperative pathological diagnosis was well differentiated papillary adenocarcinoma, T1, N0, M0, stage I) 10 years ago when he was 62 years of age. The gene discussed is MUC5AC; the disease is papillary adenocarcinoma.