1. To learn about classification of cystic pancreatic neoplasms.
2. To appreciate the classification of IPMNs.
3. To understand the diagnostic imaging findings of IPMNs.
Most pancreatic neoplasms with a predominantly intraductal growth pattern are intrapancreatic mucinous neoplasms (IPMNs), which can be classified according to the involvement of the main pancreatic duct or its side branches. There are also much less common solid intraductal tubulovillous neoplasms. IPMNs are characterised by intraductal proliferation of mucin-producing cells arranged in papillary formations. Duct dilatation due to mucin production is the pathological and radiological hallmark. IPMNs demonstrate varying degrees of dysplasia and varying cellular differentiation, with a recognised adenoma-carcinoma sequence. Pancreatic, intestinal and oncocytic cell types are mostly seen in main duct IPMNs, which have a much higher risk of invasive carcinoma than the more common branch duct IPMN, which are usually of gastric differentiation. Branch duct IPMNs are the most common cause of incidental pancreatic cysts. Imaging features such as luminal communication with the main pancreatic duct and pathological/biochemical analysis of cyst fluid can help to distinguish branch duct IPMNs from other causes of pancreatic cysts. Because of the risk of malignant transformation, prolonged imaging surveillance is recommended for individuals with branch duct IPMNs who would be potential candidates for pancreatic surgery. Worrisome features on surveillance include the development of solid or nodular enhancing components, interval enlargement of cysts and dilatation of the main pancreatic duct or common bile duct.
1. To understand diagnostic imaging findings of other cystic neoplasms.
2. To appreciate differential diagnosis of pancreatic cystic lesions.
3. To understand the follow up of cystic pancreatic neoplasms.
Cystic pancreatic lesions have a prevalence that ranges from 2,6 to 19.6% and increases with patient’s age.
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 symptomatic, 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 appear as unilocular cysts, microcystic lesions, macrocystic lesions, and cysts with solid components.