What are the different types of pancreatic mucinous cystic neoplasms?
Pancreatic mucinous cystadenoma (and cystadenocarcinoma) is a rare mucinous epithelial pancreatic neoplasm which may range from premalignant to frankly malignant. This tumor most commonly occurs in the pancreatic body or tail and is typically encountered in middle-aged women. On cross-sectional imaging, a unilocular or multilocular cystic lesion in the pancreas is seen, typically containing <6 clustered cystic foci that are >2 cm in size, sometimes with variably increased attenuation, increased T1-weighted signal intensity, or decreased T2-weighted signal intensity of the internal fluid contents. Wall thickening, septal thickening, mural nodules, solid enhancing components, or peripheral calcifications may sometimes be present. However, no communication between the lesion and the pancreatic ductal system is seen. Mesenteric vascular encasement, regional lymphadenopathy, or distant metastatic disease may be encountered in some patients as well.
Intraductal papillary mucinous neoplasm (IPMN) is an uncommon mucinous epithelial pancreatic neoplasm which may range from premalignant to frankly malignant. This tumor most commonly occurs in the pancreatic head and uncinate process and is often encountered in elderly men. There are two subtypes of IPMN: the main pancreatic duct subtype (which may also involve the side branches) and the side branch subtype; the former is more likely to be malignant than the latter. On cross-sectional imaging, the main pancreatic duct subtype typically appears as segmental or diffuse main pancreatic duct dilation (typically out of proportion to the degree of pancreatic parenchymal atrophy), sometimes with side branch dilation or bulging of the duodenal papilla. The side branch subtype typically appears as a unilocular or multilocular cystic lesion in the pancreatic head or uncinate process that communicates with the pancreatic ductal system. Wall thickening, septal thickening, mural nodules, and solid enhancing components may sometimes be present, although calcifications are not generally seen. Patients with pancreatic IPMN also have an increased risk (5% to 10%) of developing a metachronous pancreatic adenocarcinoma in the future.