The treatment of cystic pancreatic lesions of different nature is very different, and how to correctly distinguish between non-neoplastic and neoplastic lesions is the focus of clinicians’ work. EUS can clearly show cystic pancreatic lesions and has good resolution of the pancreatic parenchyma and pancreatic ducts in the tissue surrounding the pancreatic cyst. EUS-guided fine-needle aspiration biopsy (EUS-FNA) can also aspirate the cystic fluid for correlation analysis to clarify the nature of the lesion, and is also of great value in the treatment of cystic lesions of the pancreas. The cystic lesions of the pancreas treated by EUS-FNA in our hospital are reported below. I. Data and methods 1. General data: From March 2007 to April 2010, EUS-FNA was performed in 10 patients with unclear diagnosis of cystic occupying lesions of the pancreas considered by ultrasound, CT or MRI of the abdomen. 6 patients were male and 3 were female, aged 54-85 years old, average 67 years old. 9 cases had abdominal pain as the main manifestation, including 2 cases with jaundice and 2 cases with fever. 2 cases; 1 case showed only vomiting. 2. Instruments and equipment: Pentax EPM-3500 endoscopic mainframe, EG-3830 UT linear array endoscopic ultrasonograph, Hitachi EUB-5500 color ultrasonograph, COOK EUSN-22-GA, 19G-T endoscopic ultrasound puncture needle. 3. Operation method: Patients were prepared for the procedure according to painless gastroscopy, and important structures such as blood vessels were avoided under the guidance of endoscopic ultrasound, and the most suitable puncture path was chosen to pierce the puncture needle into the lesion, and a negative pressure syringe was connected to maintain a constant negative pressure, and the puncture needle was repeatedly punctured in the lesion several times under ultrasound observation. The obtained tissue strips were fixed with formaldehyde and sent for pathological examination, and the tissue fluid was sent for biochemical and routine laboratory smears and fixed with 75% ethanol spray for cytological examination. In patients with cyst drainage through the gastric wall, the cyst was punctured with a COOK 19 G–T puncture needle under EUS endoscopic ultrasound guidance, and 40 ml ml of cyst fluid was withdrawn for laboratory examination, followed by insertion of a zebra guidewire into the cyst, insertion of a needle incision knife with electricity into the cyst by a patrolling guidewire, withdrawal of the incision knife, dilatation of the gastric wall and cyst wall channel with a biliary dilatation tube, and placement of a 10 F double pigtail drain by a patrolling guidewire to drain the cyst. The cystic fluid was drained into the stomach, and a total of 200 ml of cystic fluid flowed out. 4. Diagnostic basis: The diagnosis was confirmed based on EUS ultrasound endoscopic features, cyst fluid results (properties, amylase, lipase, CEA, CA19-9, bacterial smear, cytology), and some of the operated patients were confirmed based on postoperative pathology. The diagnosis of pseudocyst was made in 4 cases, including 1 case of pancreatic cyst with gastric drainage; 4 cases of mucinous adenocarcinoma, including 1 case of complicated infection; 1 case of intraductal papillary mucinous adenoma (IPMN). neoplasm (IPMN); 1 case of pancreatic abscess. 2, EUS features: 4 cases of pancreatic pseudocysts showed homogeneous hypoechoic lesions, one of which was 3 cysts and the other 3 cases were single cysts with no separation in the cystic lumen, 3 cases had thicker cystic walls and 1 case was thinner. Two of these four patients had a previous history of pancreatitis. The mucinous cystic adenocarcinoma was located in the head (1 case), body (1 case) and tail (2 cases) of the pancreas, and was anechoic or hypoechoic, with single or multiple compartments separated by a thickened cyst wall, which could have papillary bulges within the wall, and the cyst did not communicate with the main pancreatic duct, and no dilation of the pancreatic duct was seen (Figure 1). IPMN was located in the head of the pancreas, with a single room, mixed hypoechoic, unsmooth cyst wall, and papillary bulges within the wall, which communicated with the main pancreatic duct, and a significant dilation of the pancreatic duct was seen . Pancreatic abscesses show inhomogeneous hypoechoic, multi-room with separation and thick cyst wall. 3. Cyst fluid analysis: cyst fluid in patients with pseudocysts can be transparent and can be bloody, with amylase fluctuating from 84 to 43 293 U/L, CEA and CA19-9 are low, and foam-like histiocytes are individually detected. Mucinous adenocarcinoma cystic fluid was clear, mucinous and brown in one case each, and yellowish-white pus in those with infection. CEA and CA19-9 were significantly elevated, while amylase and lipase levels were low, and cytologic examination of cystic fluid found nuclear heterogeneous cells in three cases, and mucinous cells in one case. Pus cells were found in pancreatic abscess and mucous cyst adenocarcinoma with infection, and the bacterial smear was positive. IPMN cyst fluid showed jelly-like white mucus, amylase and CEA were elevated, and nuclear heterotypic cells were found on cytological examination. 4. Treatment and regression: all patients did not have complications such as bleeding, perforation and infection associated with EUS-FNA. In three of the four cases of pseudocysts, the cysts were aspirated by direct negative pressure suction with a puncture needle, and the cysts shrank significantly after aspiration, with the maximum diameter reduction exceeding 65% in all cases, so the stents were not placed for drainage, and in one of them, a review one week later revealed an increase compared with the measured value after aspiration, but it was still significantly smaller than before puncture, and it disappeared after one year of follow-up. The patient’s abdominal pain disappeared and the abdominal distension was significantly reduced. 1 week later, the ultrasound showed that the cyst compression of the stomach disappeared and the cyst had a tendency to shrink, and is still under follow-up. In the patient with pancreatic abscess, after 2 weeks of adequate fluid extraction and intravenous antibiotics, the abdominal pain and fever disappeared completely, and the ultrasound and EUS cyst disappeared at the time of discharge and 3 months after discharge without recurrence. 1 patient with mucinous adenocarcinoma and IPMN was discharged after successful resection of the tumor after referral to surgery, and is still being followed up, and there is no recurrence yet. The other 3 patients with mucinous adenocarcinoma gave up treatment for personal reasons. Discussion Cystic lesions of the pancreas are classified into pseudocysts, true cysts and cystic tumors based on the presence or absence of epithelial tissue in the cyst wall. Pseudocysts are the most common, accounting for more than 70% of all cystic lesions, and true cysts account for a small proportion of cystic lesions. Cystic tumors of the pancreas account for about 1% of pancreatic tumors and 10% to 30% of cystic lesions of the pancreas, mainly including benign plasmacytoma, potentially malignant or malignant mucinous cystadenoma, mucinous cystadenoma, intraductal papillary mucinous adenoma, and rarely, solid pseudopapillary tumors and cystic carcinoid tumors. For cystic lesions of the pancreas, the first thing to determine is whether it is a pseudocyst or a cystic tumor, and the second thing to determine whether the cystic tumor is benign or malignant. EUS-FNA can not only clearly show pancreatic cystic lesions, but also has good resolution of pancreatic parenchyma and pancreatic ducts around pancreatic cysts, and can aspirate cystic fluid for relevant analysis, so it is an effective method for preoperative diagnosis of cystic tumors. Pseudocysts are often complicated by acute or chronic pancreatitis or abdominal trauma and often appear as a single independent hypoechoic mass with no separation or solid components in the cystic cavity, thick cystic wall, but usually <4 mm, and 65% of cysts are connected to the pancreatic duct. The cystic fluid is often colorless and hyperviscous, and may be mucinous or bloody if complicated by infection and bleeding. High amylase and low CEA concentrations are characteristic of their cystic fluid, but there are individuals with no high amylase. The threshold value of amylase in cystic fluid is determined by different experimental standards at home and abroad. A foreign study found that the possibility of pseudocysts with amylase concentration <250 U/L in the cyst fluid is small, but another study found one case of pseudocysts with amylase concentration of 115 U/L. The amylase in the cyst fluid of four cases of pseudocysts at our institution fluctuated from 84 to 43 293 U/L. CEA <5 ng/mL distinguished pseudocysts or plasmacytic cystadenomas from mucinous tumors and IPMN with a sensitivity of 50%, specificity of 95%, positive predictive value of 94%, negative predictive value of 55%, and accuracy of 67%. The CEA concentrations of the four cases of pseudocysts diagnosed in our hospital were not high, which was consistent with the literature. Cytologic examination of the cyst fluid of pseudocysts sometimes revealed macrophages or neutrophils. Pseudocysts can regress on their own after adequate aspiration and drainage, so being able to make a correct diagnosis can avoid blind surgery. Plasmacytoid cystadenoma is a benign tumor, and mucinous cystic lesion is a potentially malignant tumor. Peripheral calcification, papillary elevation within the cyst wall, and vascular encapsulation often suggest malignant lesions. CEA >800 ng/mL distinguishes mucinous from plasmacytic lesions with a sensitivity of 48%, specificity of 98%, positive predictive value of 94%, negative predictive value of 75%, and accuracy of 79%. The value of CEA was set at 192 ng/mL in a multicenter trial, which had the highest accuracy in differentiating the two types of disease. In this paper, all four cases of mucinous cystadenocarcinoma had a CEA greater than 1000 ng/mL. cytologic examination of plasmacytoid cystadenoma is usually glycogen-rich cells, whereas mucinous lesions are mucus-rich cells, and malignant tumors are often found to have nuclear heterotypic cells. However, sometimes it is not easy to distinguish the two types of disease by ultrasound presentation and cystic fluid characteristics alone, and the final diagnosis needs to be confirmed by surgical pathological biopsy. IPMN originates from the main pancreatic duct or branch pancreatic ducts, preferably in the head of the pancreas. Dilation of the pancreatic duct and a large amount of mucus collects in the pancreatic duct, and sometimes mucus is seen to overflow from the papilla. IPMN occurring in the body and tail of the pancreas is sometimes difficult to distinguish from mucinous cystadenoma, and whether it is connected to the pancreatic duct and whether the pancreatic duct is dilated can be used as a differentiator. The usually high amylase content in the cystic fluid is also one of the differentiating points. In this paper, one case of IPMN was located in the head of the pancreas, and the pancreatic duct was seen to be significantly dilated, and a large amount of mucus was punctured by EUS-FNA, which was finally confirmed as IPMN by cytology and surgical pathology. Pancreatic abscesses often present with unexplained abdominal pain, fever and jaundice, and the temperature does not decrease even after intravenous antibiotics, because of the low local concentration of antibiotics in the pancreas and the thick wall of the abscess. With the help of EUS-FNA, the pus in the abscess can be basically aspirated and the lesion can be eliminated rapidly, and with the intravenous antibiotics, the patient can be cured quickly. Most pancreatic pseudocysts heal spontaneously, but they need to be treated when they keep growing, or when they become symptomatic, complicated by infection or bleeding. Surgery was once the only treatment for pseudocysts, and now EUS transgastric or duodenal drainage is gradually being performed in China and abroad. As a minimally invasive technique, it is a safe and effective treatment method by selecting an appropriate puncture site and supplementing it with dilation and tube placement for drainage. In this paper, three cases of pseudocysts were significantly reduced or even disappeared after aspiration, while one case of giant cyst was ducted through the stomach, and although it is still under observation, the cyst regression and the patient’s quality of life were excellent. The prognosis of pancreatic cystic lesions is generally better than that of pancreatic cancer. Compared with traditional percutaneous puncture, EUS-guided fine needle puncture of the pancreas has a shorter puncture route, fewer complications, and is safe and practical.