Pancreatic cystic tumors: an update

Abstract Pancreatic cystic tumors (PCTs) comprise a heterogeneous group of entities, accounting for 2% to 10% of pancreatic lesions. The most common types are intraductal papillary mucinous neoplasms (IPMNs), mucinous cystic neoplasm (MCN), and serous cystic neoplasm (SCN), which account for approximately 90% of PCTs. This review discusses updates in pathologic features, malignant transformation, biologic behavior, and molecular evolution of PCTs. IPMN includes main duct and branch duct types. These can also be classified into 4 histologic subtypes based on cell lineages of differentiation, and may be associated with different tumorigenic pathways and clinicopathologic characteristics. The gastric type is the most common and is rarely associated with carcinomas, whereas the pancreatobiliary type is significantly more associated with invasive carcinoma. MCN is a mucinous cystic lesion with the presence of ovarian-type pericystic stroma. Prognosis of the resected non-invasive MCN is excellent, but the long-term survival of MCNs with invasive carcinoma may be poor. SCN includes microcystic adenoma, macrocystic adenoma, and solid variant serous adenoma. Serous cystadenocarcinoma is defined by the presence of distant metastases, which is rare in literature. Intraductal tubulopapillary neoplasm is characterized by uniformly high-grade dysplasia and ductal differentiation without overt production of mucin, with high risk for developing invasion. Acinar cell cystadenoma is a rare benign lesion with acinar differentiation. In addition, some pancreatic neuroendocrine tumors may assume a cystic configuration, sometimes referred to as cystic pancreatic endocrine neoplasm tumor, with a lower pathologic stage. Solid pseudopapillary tumor is composed of poorly cohesive monomorphic epithelial cells forming solid and pseudopapillary structures, with excellent prognosis.