Malignant transformation of branch duct-type intraductal papillary mucinous neoplasms of the pancreas based on contrast-enhanced endoscopic ultrasonography morphological changes: Focus on malignant transformation of intraductal papillary mucinous neoplasm itself

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.