Risk Factor for Appearance of Invasive Carcinoma During Follow Up in Branch Duct Type IPMN

Introduction: The presence of mural nodule (MN) is an important factor for the management of branch duct type intraductal papillary mucinous neoplasm (BD-IPMN).International consensus guidelines 2012 recommend clinical follow-up to BD-IPMN without MNs.However, it is not clear whether BD-IPMNs with MNs need surgical treatment regardless of the height of MNs.Aim: To compare the pathological and follow-up outcomes between BD-IPMNs with MNs ≤6mm in height (MN+) and those without MNs (MN-).Methods: The patients who were diagnosed as BD-IPMNs with MNs ≤6mm or without MNs since April 2004 to December 2013 were retrospectively analyzed.Inclusion criteria were the obtaining of contrast enhanced CT and EUS at initial diagnosis, and surgical resection in our center or follow-up with annual/semi-annual CT/MRCP.The cyst size and main pancreatic duct (MPD) diameter were measured by CT/MRCP, while MN height was measured by EUS.Tumor progression during follow-up was defined as follows; increased cyst size ≥10mm; increased MPD diameter ≥10mm; new development of MN or increased MN height ≥2mm.Evaluation points: 1) pathological diagnosis of resected BD-IPMN, 2) follow-up outcomes Results: Among 656 patients of BD-IPMNs diagnosed in our center, MN height was evaluated as less than or equal to 6mm in 511(78%; MN+ 50, MN-352).After initial diagnosis, 17(3%; MN+ 8, MN-9) of them underwent immediate resection and 385(75%; MN+ 42, MN-343) of them received regular follow-up, who were eligible for this analysis.The median cyst size and MPD diameter were 20(10-70) mm and 3(2-12) mm, respectively.The median height of MNs in MN+ were 3(1-6) mm. 1) The pathological diagnosis of the patients with MN-were all low/intermediate-grade dysplasia (LID), while those of the patients with MN+ were LID in 5, high-grade dysplasia (HD) in 2, and invasive carcinoma (IC) in 1.There were no significant differences in pathological diagnosis between MN+ and MN-(p=0.17,chi-square test).2) During a median follow-up period of 3.4(0.5-10.6)years, 49(13%; MN+ 9, MN-40) patients exhibited tumor progression.The 5-years cumulative tumor progression rate was higher in MN+ than those in MN-(MN+ 19% vs MN-9%; p<0.01,Log-rank test).Among 49 patients with tumor progression, 11(22%; MN+ 4, MN-7) patients underwent surgical resection, whose pathological diagnosis were LID in 6(MN+ 2, MN-4), HD in 3(MN+ 1, MN-2), and IC with minimal invasion in 2(MN+ 1, MN-1).The other 38 patients continued to be followed during a median period of 0.6(0.0-4.2) years.Meanwhile, concomitant pancreatic ductal adenocarcinoma (PDAC) was appeared in 9(2%; MN+ 1, MN-8) patients.Conclusion: Although tumor progression rate was higher, BD-IPMN with MNs ≤6mm in height on EUS could be managed conservatively.However, careful attention should be paid to the development of PDAC during follow-up.