Malignant Transformation of Branch Duct–Type Intraductal Papillary Mucinous Neoplasms of the Pancreas Based on Contrast-Enhanced Endoscopic Ultrasonography Morphological Changes

Objectives The natural history of branch duct–type intraductal papillary mucinous neoplasms (BD-IPMNs) of the pancreas remains unclear. We conducted a retrospective long-term follow-up study for malignant transformation (MT) of BD-IPMNs focusing on morphological changes. Methods The subjects consisted of 142 patients who underwent contrast-enhanced endoscopic ultrasonography for initial diagnosis from January 2001 with more than 12 months of follow-up. The MT rate, including the co-occurrence of invasive ductal cancer, was evaluated by univariate and multivariate analysis. In addition, on the basis of morphological changes in patients who underwent surgery, the predictive factors for malignant IPMNs were evaluated. Results Median follow-up term was 42.5 months (range, 12–105 months). Thirty patients who exhibited morphological changes underwent surgery. Malignant transformation occurred in 9 patients (6.3%), and 5-year MT rate was 10.7%. The co-occurrence of invasive ductal cancer was seen in 5 patients. Multivariate analysis showed that the existence of mural nodules at initial diagnosis and involvement of main pancreatic duct were significant predictors of MT of BD-IPMN. Conclusions Malignant transformation of BD-IPMN is not rare. The observation of morphological changes of main pancreatic duct and nodules, mainly on contrast-enhanced endoscopic ultrasonography, is practical and useful for predicting MT of BD-IPMN itself. Abbreviations IPMN - intraductal papillary mucinous neoplasm BD-IPMN - branch duct–type intraductal papillary mucinous neoplasm MT - malignant transformation IDC - invasive ductal cancer MPD - main pancreatic duct CE-EUS - contrast-enhanced endoscopic ultrasonography EUS-FNA - endoscopic ultrasonography–guided fine needle aspiration MD-IPMN - main duct–type intraductal papillary mucinous neoplasm MD-CT - multidetector row computed tomography HR - hazard ratio OR - odds ratio