Pancreatic Ductal Adenocarcinoma Concomitant with Main Duct Type Intraductal Papillary Mucinous Neoplasm of the Pancreas: A Case Report.

BACKGROUND Intraductal papillary mucinous neoplasm of the pancreas (IPMN) and pancreatic ductal adenocarcinoma (PDAC) often coexist in the same pancreas. Almost all IPMNs involving PDACs concomitant with IPMN have been shown to be branch duct type IPMNs (BD-IPMNs), and their histological subtypes are gastric type. Therefore, PDACs concomitant with main duct type IPMNs (MD-IPMNs) are considered to be rare. We herein report a rare case preoperatively diagnosed as being a PDAC concomitant with MD-IPMN on the basis of imaging findings and histological findings of pancreatic specimens endoscopically obtained from 2 lesions. CASE REPORT A 67-year-old man was referred to our hospital due to an enlarged pancreas. Using imaging studies, a solid mass was found in the pancreatic head and intraductal papillary masses in the dilated main pancreatic duct of the body and tail with a fistula in the duodenum. On the basis of histological results using specimens endoscopically obtained from each of the 2 lesions, total pancreatectomy was planned due to suspected PDAC concomitant with an MD-IPMN. Finally, resected specimens were used to confirm the presence of a rare case of PDAC concomitant with MD-IPMN. CONCLUSIONS We encountered a rare case of a PDAC concomitant with an MD-IPMN which could be preoperatively diagnosed by using imaging studies and histological specimens endoscopically obtained. In addition to invasive cancers derived from IPMNs, PDACs concomitant with IPMNs can rarely develop in the pancreas involving MD-IPMNs.