Advance in study on diagnosis of pancreatic cystic tumors on CT/MRI imaging

Abstract

Pancreatic cystic tumors (PCN) refer to cystic tumor lesions originating from the epithelium and/or interstitial tissue of the pancreatic duct. PCN can be roughly divided into mucinous tumors and non-mucinous tumors. The former mainly includes intraductal papillary mucinous neoplasms (IPMN) and mucinous cystic neoplasms (MCN), while the latter mainly includes serous cystic neoplasms (SCN) and solid-pseudopapillary neoplasms (SPN) and cystic neuroendocrine neoplasms (cNET). Different types of PCNs have differentiated biological behaviors, and some types of PCNs have a risk of developing a malignancy. Preoperative identification of PCN malignancy on CT and MRI imaging is of great significance. Malignant indications for MCN are surgical indications， such as a diameter greater than or equal to 4 cm. IPMN accounts for 22% of PCN, and the risk of malignancy in main pancreatic duct type and mixed type IPMN can reach up to 70.9% and 76.5%, while the risk of malignancy in branch pancreatic duct type IPMN is 2.8%-10.7%. High risk signs of malignancy for IPMN include enhanced parenchymal or diameter of parietal nodules ≥ 5 mm, main pancreatic duct dilation (≥ 10 mm), and obstructive jaundice, and surgical treatment is recommended for these patients. SCN is more common in middle-aged and elderly women, with a male to female ratio of 1:3. Serous cystadenocarcinoma is rare, accounting for only 0.1% of pancreatic SCN. The 2015 edition of the Diagnosis and Treatment Guidelines for Pancreatic Cystic Diseases recommends that all SPNs patients should undergo surgical treatment. When the tumor of SPN with incomplete capsule, the mass diameter larger than 6 cm, and the tumor located in the tail of the pancreas, may have a higher ability of invasiveness and distant metastasis. cNET accounts for approximately 7% of PCN. Imaging diagnosis should be combined with medical history and lesion components, etc. The diagnostic point for SPN on image is that MCN is a round, thick walled cystic tumor that almost exclusively occurs in females in the body and tail of the pancreas body, often presenting as an “intracystic cyst”. IPMN is more common in elderly men. The main pancreatic duct type of IPMN presents as diffuse or segmental dilation of the main pancreatic duct, excluding obstructive factors. Branch pancreatic duct type of IPMN usually presents as tubular cystic tumors that communicate with the pancreatic duct, while mixed type of IPMN combines both manifestations. SCN is a lobulated, thin-walled oligocystic or multicystic honeycomb tumor. SPN is a larger round cystic solid tumor that is more common in young women. cNET is a cystic solid tumor with significantly enhanced circular or crescent shaped edges. There is significant controversy in domestic and foreign guidelines regarding the selection of indications for PCN surgery, and pancreatic surgery is difficult with many postoperative complications, posing challenges to the standardized treatment of PCN. Identifying the imaging characteristics of PCN and clarifying imaging diagnosis has clinical significance.

Keywords

• |pancreatic cystic neoplasm|imaging diagnosis|computed tomography|magnetic resonance imaging