Duodenal cancer arising from the remaining duodenum after pylorus-preserving pancreatoduodenectomy for ampullary cancer in familial adenomatous polyposis.

We herein report a rare occurrence of duodenal cancer arising from the remaining duodenum after pylorus-preserving pancreatoduodenectomy for ampullary cancer in familial adenomatous polyposis (FAP). In this patient, proctocolectomy and ileoanal anastomosis for FAP had been performed 11 years earlier. During the current admission, the patient was diagnosed with adenocarcinoma in the Vater's ampulla using imaging and pathological examinations. In addition, a pylorus-preserving pancreatoduodenectomy was performed. The tumor was a well-differentiated tubular adenocarcinoma and no other polyps were identified in the duodenum by pathological examination. However, 1 year after surgery, a polypoid lesion measuring 15 x 15 mm was indicated in the remaining duodenum by endoscopic surveillance. This lesion was completely resected by endoscopic mucosal resection and the resected specimen revealed well-differentiated tubular adenocarcinoma in an adenomatous lesion. This report suggests that resection of the total duodenum is essential for duodenal neoplasms in FAP to prevent a recurrence in the remaining duodenum.