Department of Gastroenterology and Hepatology, Kindai University Faculty of Medicine
Background and Aim: Pancreatic ductal adenocarcinomas（PDACs）concomitant to or derived from branch duct intraductal papillary mucinous neoplasms（IPMNs）sometimes arise in patients with IPMNs. The usefulness of endoscopic ultrasonography（EUS）relative to other imaging methods for detecting these tumors was assessed. Patients and methods: In 2003-2015, 202 consecutive patients with IPMNs were followed up by EUS, ultrasonography（US）, computed tomography（CT）and magnetic resonance imaging（MRI）. If one of the four modalities showed during follow-up that the cystic lesion had changed or a nodule had appeared, the other three modalities were performed within the following month. The following outcomes were evaluated:（i）frequencies of changes in the IPMNs and the new development of IPMN-derived and IPMN-concomitant PDACs during follow-up;（ii）the relative sensitivity with which each imaging modality depicted PDAC during follow-up;（iii）characteristics of patients with IPMN-concomitant PDACs. 【Results】 The 202 patients with IPMNs were on average 67-years-old and the ratio of males to females was 88:114. IPMNs with high-risk stigmata and worrisome feature were seen in 24 and 50 patients at the initial diagnosis. Median follow-up period was 44 months．（i）In 36 of the 202（17.8％）followed-up patients, changes in the IPMNs were seen during follow-up: dilation of cystic lesion≥10 mm; n=12, appearance or increase of a nodule; n=15, appearance of thick septa; n=7 and dilation of main pancreatic duct≥2 mm; n=2. Eight IPMN-concomitant PDACs and two IPMN-derived invasive PDACs were developed during follow-up．（ii）EUS, US, CT and MRI achieved depiction of IPMN-concomitant PDACs in 100％（8/8）, 13％（1/8）, 38％（3/8）and 38％（3/8）, respectively whereas these four modalities achieved depiction of IPMN-derived PDACs in 100％（2/2）, 50％（1/2）, 50％（1/2）and 50％（1/2）, respectively．（iii）All IPMN-concomitant PDACs were detected at an operable stage, but one patient rejected surgical resection because of his advanced age and underwent chemotherapy instead. While approximately two-thirds of the IPMNs of all of these cases were located in the pancreatic head, IPMN-concomitant PDACs showed an opposite orientation: seven PDACs were located in the body or tail. All concomitant IPMNs were branch duct IPMNs without mural nodules. The concomitant PDACs were on average 15mm in maximum diameter and three were stage I whereas four were stage II and one was stage III. In the eight patients whose PDACs were detected during follow-up, the longest diameter of the dilated branch duct and the width of the pancreatic duct at the first examination were 13mm and 4mm, respectively. These duct dimensions did not increase during follow-up. 【Conclusions】 IPMN-concomitant PDACs are quite often found during follow-up. EUS examination of the whole pancreas plays an important role in the management of IPMNs as it allows the early detection of these small invasive carcinomas.