Cyst growth rate predicts malignancy in patients with branch duct intraductal papillary mucinous neoplasms

Little information is available about the clinico-pathologic characteristics of pancreatic branch duct intraductal papillary mucinous neoplasm (Br-intraductal papillary mucinous neoplasm [IPMN]) because of difficulties in diagnosis based on radiologic and tissue information. We investigated the natural history of Br-IPMN using imaging and surgical pathology data from patients.

Data were collected from patients admitted to a single tertiary referral institution from January 2000 to March 2009 (median follow up of 27.9 months); 201 patients were diagnosed with Br-IPMN with an initial cyst less than 30 mm without main pancreatic duct dilatation or mural nodules. The patients were followed for more than 3 months and examined by computed tomography (CT) at least twice.

The mean size of the patients' initial cysts was 14.7 mm; the mean cyst growth rate was 1.1 mm/year. Thirty-five patients received surgery during follow up and 8 were confirmed to have malignant cysts. The malignant cysts were greater in final size than nonmalignant cysts (24.3 mm vs 16.9 mm; P = .003); they also grew by a greater percentage (69.8% vs 19.4%; P = .046) and at a greater rate (4.1 mm vs 1.0 mm/year; P = .001). The actuarial 5-year risk of malignancy was 41.6% in the group that received surgery and 10.9% for all patients. Cysts that grew more than 2 mm/year had a higher risk of malignancy (5-year risk = 45.5% vs 1.8%; P < .001).

In combination with cyst size and the presence of mural nodules, cyst growth rate could be used to predict malignancy in patients with Br-IPMN.