Background: Synchronous occurrence of intraductal papillary mucinous neoplasm (IPMN) and ductal carcinoma of the pancreas has been reported. Branch duct IPMNs with lower likelihood of malignancy are not submitted to resection but are followed up, so ductal carcinoma may develop during the follow-up. We investigated the development of ductal carcinoma of the pancreas during follow-up of branch duct IPMNs.
Patients and Methods: Sixty patients of branch duct IPMN that had intraductal tumor of less than 10mm on imaging examinations and negative result for malignancy in cytologic examination of pancreatic juice were investigated. They were followed up mainly by ultrasonography (US), and additionally by endoscopic ultrasonography (EUS), computed tomography (CT), magnetic resonance cholangiopancreatography (MRCP), or endoscopic retrograde cholangiopancreatography (ERCP) with cytologic examination of pancreatic juice for an average period of 87 months.
Results: Ductal carcinoma of the pancreas distinct from IPMN developed in 5 of 60 (8%) branch duct IPMNs during follow-up. 5-year rate of development of ductal carcinoma was 6.9% (95%CI 0.4-13.4%), incidence of ductal carcinoma was 1.1% (95%CI 0.1-2.2%) per year, and standardized incidence ratio of development of ductal carcinoma was 26 (95%CI 3-48). Patients over 70 years old developed ductal carcinoma significantly more frequently than those under 69. Four of 5 ductal carcinomas identified during follow-up were resectable. Cancer developed in IPMN in 2 of 60 (3%) branch duct IPMNs during follow-up.
Conclusions: During follow-up of branch duct IPMNs ductal carcinoma of the pancreas not infrequently developed apart from IPMN. In the follow-up of IPMN, special attention should be paid to the development of ductal carcinoma of the pancreas.