Vanishing Pancreatic Cysts during Follow-Up: Another Step Towards De-Emphasizing Cyst Size as a Major Clinical Predictor of Malignancy

Introduction: In the management of pancreatic cystic neoplasms (PCN), size plays a crucial role as the expression of disease progression. While many evidences regarding the natural history of growing pancreatic cysts exist, almost no data are available regarding cysts with a reduction in size. Methods: Radiological and clinical data from patients of the dedicated pancreatic cysts outpatient clinic of the Department of General and Pancreatic Surgery, University of Verona Hospital were retrospectively reviewed. Patients diagnosed with PCNs reducing in size during follow-up were reviewed. Results: From a total of 3,146 patients, we identified 12 (0.38%) vanishing/reducing cysts without a history of pancreatitis. Most of them were presumed IPMN (66.6%). The median follow-up was 69 months and the median cyst's size 30 mm (range 10-49). Most of the patients (75%) experienced a reduction in cyst size (median reduction of 8 mm, range 6-22) after a median time of 12 months (range 6-63), 3 patients experienced a complete disappearance of the cyst. Conclusion: Cyst size reduction during follow-up is a rare phenomenon of unknown explanation. It adds to the debate regarding the role of size as a clinical predictor whenever a definite diagnosis of a PCN cannot be reached.