Long-term follow-up of neoplastic pancreatic cysts without high-risk stigmata: how often do we change treatment strategy because of malignant transformation?

*Objective: Patients with potentially premalignant neoplastic pancreatic cysts without high-risk stigmata usually enter a surveillance program. Data on outcomes of such surveillance programs are scarce. We aimed to evaluate the resection rate and malignancy rate during follow-up.Material and methods: From our prospective database (2006-2015) of patients with pancreatic cysts, we analyzed patients with pancreatic cysts without high-risk stigmata with at least six months follow-up.Results: In total, 146 patients were followed for a median of 29 months (IQR 13.5-50 months). In 124 patients (84.9%), no changes in clinical or imaging characteristics occurred during follow-up. Thirteen patients (8.9%) developed an indication for surgery after a median follow-up of 25 months (IQR 12-42 months). Two patients did not undergo surgery because of comorbidity, 11 patients (7.5%) underwent resection. Indications for surgery were symptoms (n=2), development of a pancreatic mass (n=1), a new nodule (n=2), thickened cyst wall (n=1), pancreatic duct dilation (n=3), and/or suspicion of mucinous cystic neoplasm (MCN) (n=3). Postoperative histology showed one pancreatic malignancy not originating from the cyst, three mixed type-intraductal papillary mucinous neoplasm (IPMN), one side branch-IPMN, two MCN, one neuroendocrine tumor, one serous cystadenoma, one inflammatory cyst, and one lymphangioma. The highest grade of cyst dysplasia was borderline dysplasia.Conclusions: Most neoplastic pancreatic cysts without high-risk stigmata at initial presentation show no substantial change during 1-4-year follow-up. Only 7.5% of patients underwent surgery and less than 1% of patients developed pancreatic malignancy. This indicates that additional markers are needed to tailor treatment of pancreatic cysts.