Morphologic Changes in Branch Duct Intraductal Papillary Mucinous Neoplasms of the Pancreas: A Midterm Follow-Up Study

Background & Aims: Because there is a low risk of malignancy for intraductal papillary and mucinous neoplasms of the pancreas (IPMNs) confined to branch ducts (BD), patient follow-up evaluation without surgery is possible. The aim of this study was to assess time-related morphologic changes and risk of progress to malignancy in patients with BD IPMN. A prospective design was used in an academic tertiary referral center. Methods: All consecutive patients seen from 1999 to 2005 with highly suspected IPMNs confined to BD without criteria suggesting a malignant development (mural nodule, cyst wall thickness >2 mm, BD diameter >30 mm, or main pancreatic duct involvement) were followed up prospectively using computerized tomography, magnetic resonance cholangiopancreatography, and endoscopic ultrasonography. Results: A total of 121 patients (median age, 63 y) were included. After a median follow-up period of 33 months, no morphologic changes had occurred in 88 patients. The size of the cyst increased in 30 of the 33 remaining patients, and 12 developed criteria suggesting a malignant development. Surgery, performed in 8 of 12 patients, found 4 IPMN-adenomas, 1 borderline-IPMN, and 4 IPMN carcinoma in situ. The 4 remaining patients did not undergo surgery because of severe comorbid conditions in 2, change in reference hospital in 1, and a mural nodule considered being sequelae of previous fine-needle aspiration in 1 patient. The only factor associated with signs suggesting malignant development was an increase in cyst size to more than 5 mm during the follow-up evaluation. Conclusions: In patients with IPMNs confined to BD, morphologic changes are rare events, justifying a nonsurgical approach. Careful follow-up evaluation remains necessary, particularly in patients with an increase in BD size.