LEARNING OBJECTIVES 1) Describe the clinical and pathologic features of cystic pancreatic neoplasms and the key diagnostic imaging findings useful for diagnosis. 2) Indicate the radiological signs useful for the differential diagnosis. 3) Identify clinical and diagnostic imaging criteria that require follow up and the anatomical landmarks that are important for surgical treatment planning. ABSTRACT Cystic pancreatic lesions are diagnosed with increasing frequency in the general population, because of diagnostic imaging technology improvements and wide spread of cross sectional imaging studies, with a prevalence that ranges from 2,6 to 19.6% and increases with patient’s age. Approximately 90% of cystic pancreatic tumors are represented by serous cystadenoma (SCA), mucinous cystadenoma (MCA) and intraductal papillary mucinous neoplasms (IPMNs). Less frequently diagnosed cystic neoplasms of the pancreas are represented by solid pseudopapillary tumor, cystic neuroendocrine tumors, and cystic adenocarcinoma. At clinical presentation, IPMNs are diagnosed in patients presenting with symptoms, whereas SCAs and MCAs are incidentally diagnosed during diagnostic imaging examination performed because of other reasons. Cystic pancreatic neoplasms have a different biological behavior ranging from benign, border line and -malignant lesions: IPMNs and MCAs are well established precursors of invasive carcinoma, and warrant surgery. Whereas SCAs shows a benign biological and clinical course, with no indication to surgery, but to clinical-radiological follow up. Therefore the characterization of cystic pancreatic neoplasms represents a medical need in order to perform an adequate risk stratification and to avoid unnecessary surgical procedures. IPMNs originate from the mucinous epithelium of the pancreatic duct system, and are characterized by papillary growth, hyper-production of mucin causing ductal dilatation. The gross appearance of these tumors depends on the site of origin, along the pancreatic duct system: we can distinguish IPMNs of the main pancreatic duct (MPD), IPMNs of the side branches (SB), or mixed. Malignancy can occur in 30-88% of IPMNs, and the risk of malignant degeneration correlates with the site of origin of the tumor SCAs and MCAs morphologically appear as unilocular cysts, microcystic lesions, macrocystic lesions, and cysts with solid components.