Annular pancreas is a rare anomaly in which a ring of pancreatic tissue encircles the second portion of the duodenum. We herein report a case involving a 79-year-old Japanese man with an intraductal papillary mucinous neoplasm (IPMN) of the pancreas. Imaging studies showed that the pancreatic tissue encircled the descending part of the duodenum and that a 30-mm-diameter cystic tumor was present in the annular segment, leading to the diagnosis of pancreatic IPMN. Limited pancreatic resection was successfully performed by careful division of the annular segment from the second portion of the duodenum. The postoperative course was uneventful, and the patient's pancreatic function was retained without the need for supplementation. To the best of our knowledge, this is the first report of IPMN occurring in the annular segment of the pancreas. Limited resection of the pancreatic annular segment is a feasible surgical treatment for noninvasive IPMN of the annular pancreas.
Keywords: Annular pancreas; Intraductal papillary mucinous neoplasm; Partial pancreatic resection.