Pancreatic cancer is a digestive tumor with a poor prognosis, and its incidence has been on the rise worldwide in recent years. The American Cancer Society estimated that the number of new cases of pancreatic cancer in the United States in 2008 was 37,680, and the number of deaths was 34,290, ranking fourth in the mortality rate of malignant tumors, with about 75% of patients dying within 1 year after diagnosis and a 5-year survival rate of <5% [1]. The incidence of pancreatic cancer in China is also increasing year by year. Surgical resection is still the main means of treatment and long-term prognosis, but due to the insidious disease of pancreatic cancer and the lack of specific clinical manifestations in the early stage, most patients are already in the advanced stage when they are diagnosed, and only 10-20% of patients can be surgically resected [2], and the 5-year survival rate can be increased to about 15-25% after radical pancreatic cancer surgery with adjuvant radiotherapy [3], but this is still not ideal. Early diagnosis can increase the surgical resection rate and significantly improve patient prognosis. Therefore, how to improve the early diagnosis rate of pancreatic cancer under the existing medical conditions, combined with the actual national conditions in China, deserves the attention of the majority of gastroenterologists and surgeons, especially pancreatic specialists. 1, Early stage pancreatic cancer Early stage pancreatic cancer refers to T1N0M0 stage tumor with tumor confined to the pancreas, maximum diameter <2 cm, no lymph node metastasis, no infiltration of the pancreatic peritoneum and posterior pancreas, no vascular and adjacent organ invasion [4]. This is different from the definition of small pancreatic cancer, which mainly refers to tumors with a maximum diameter of <2 cm regardless of the presence of lymph node metastases. Studies have shown that tumor size is an independent risk factor in determining the prognosis of pancreatic cancer, and although small pancreatic cancer is not equal to early pancreatic cancer, the smaller the tumor size, the more likely it is to be early pancreatic cancer and the better the outcome of radical surgery. The surgical resection rate of early pancreatic cancer is 90%-100%, and the 5-year survival rate can reach 70%-100%, which is significantly better than that of progressive pancreatic cancer. Therefore, it is important to detect early pancreatic cancer or small pancreatic cancer and improve the early diagnosis and surgical resection rate of pancreatic cancer in order to improve the prognosis of patients. 2. High-risk group of pancreatic cancer and screening Early pancreatic cancer often presents with non-specific gastrointestinal symptoms or no symptoms at all. Even under the existing advanced imaging methods, the early diagnosis rate of pancreatic cancer is still very low, which is related to its own characteristics on the one hand, and the lack of due vigilance and sufficient attention of gastroenterologists and surgeons on the other hand is one of the main reasons for this situation. About more than half of the patients are misdiagnosed as gastrointestinal or hepatobiliary diseases for 3-6 months, and when the diagnosis is confirmed, most patients lose the opportunity of radical surgical resection. Therefore, for first-time patients, outpatient physicians should be aware of the possibility of pancreatic cancer and should not be satisfied with the diagnosis of chronic gastritis and functional dyspepsia, but should perform targeted examinations on these patients to reduce the misdiagnosis rate of pancreatic cancer and shorten the time to diagnosis [5]. Peking Union Medical College Hospital has established a multidisciplinary collaborative group consisting of related departments such as surgery, internal medicine, diagnostic imaging and pathology to open a green channel to ensure that patients complete the necessary examinations in the shortest possible time to achieve early diagnosis, timely treatment and improved surgical resection rate. It has been confirmed that pancreatic ductal adenocarcinoma originates from pancreatic ductal epithelial cells and gradually progresses to invasive pancreatic cancer through atypical hyperplasia, precancerous lesions to carcinoma in situ, and pancreatic intraductal neoplasm (PanIN), intrapancreatic ductal papillary mucinous neoplasm (IPMN) and mucinous cystadenoma (MCN) are three common precancerous lesions that have been confirmed [6]. Timely detection of these precancerous lesions and their resection before they progress to pancreatic cancer can significantly improve the prognosis of patients. Due to the relatively low incidence of pancreatic cancer and combined with the actual national conditions in China, large-scale screening for the general population is poorly operable and has a poor economic benefit ratio, but more purposeful screening for high-risk groups prone to pancreatic cancer is feasible and can greatly improve the early diagnosis rate of pancreatic cancer . The Pancreatology Group of the Chinese Medical Association Surgery Branch proposed the concept of high-risk groups for pancreatic cancer in the 2007 guidelines for the diagnosis and treatment of pancreatic cancer, including: 1) patients older than 40 years with non-specific symptoms in the upper abdomen; 2) those with a family history of pancreatic cancer; 3) patients with sudden onset diabetes; 4) patients with chronic pancreatitis, especially chronic familial pancreatitis and chronic calcifying pancreatitis; 5) intraductal papillary mucinous tumors; 6, those with familial adenomatous polyposis; 7, those with benign lesions undergoing major distal gastrectomy, especially those more than 20 years after surgery; 8, history of smoking, heavy alcohol consumption, and long-term exposure to harmful chemicals [7]. Foreign countries currently believe that screening for high-risk groups with a relative risk greater than 10 can benefit these patients, including: familial pancreatic cancer, P-J syndrome, hereditary pancreatitis, and familial atypical multiple nevus melanoma syndrome (FAMMM) [8]. It is still inconclusive when to start screening for these high-risk groups after identifying them for pancreatic cancer. In China, there is no experience in this area, but most foreign countries combine the relative risk of patients and refer to the experience of large centers for screening, for example, for familial adenomatous polyposis, the recommended age is 40 years or 10 years forward for the youngest patient in the family to develop the disease, while for P-J syndrome, the recommended age is 25-30 years [9]. There is also no consensus on how often to screen, and some large foreign centers have proposed some of their own criteria, such as once a year for John Hopkins and once every 2-3 years initially for the University of Washington, which changed to once a year after approaching the age of onset [8]. In addition, screening for pancreatic cancer in high-risk groups can further understand the molecular biological mechanism of pancreatic cancer development, which is of great significance for future basic research and clinical treatment. Therefore, screening for these high-risk groups is necessary and is gradually gaining attention, and relevant prospective studies are being conducted abroad to systematically evaluate the screening of high-risk groups for pancreatic cancer, such as John Hopkins, University of Washington, EUROPAC and FaPaCa [10]. 3. Early diagnosis of pancreatic cancer methods The methods of early diagnosis and screening of pancreatic cancer have been improved continuously, among which the rapid development of imaging has greatly improved the detection rate of small pancreatic cancer and early pancreatic cancer, but up to now there is still no single diagnostic method that can achieve the ideal sensitivity and specificity. Combining multiple tests can greatly improve the early diagnosis rate of pancreatic cancer. CA19-9 is the most commonly used tumor marker for the diagnosis of pancreatic cancer, but its accuracy and specificity for the diagnosis of early pancreatic cancer is poor, and for pancreatic cancer less than 2 cm in diameter, 48, 4% of patients are negative for CA19-9, and its specificity is significantly reduced [11]. MUC-1, MIC-1, NGAL, CEACAM1 are some of the tumor markers that have been reported more frequently in recent years for the early diagnosis of pancreatic cancer [13-15], and these tumor markers have shown some advantages in the diagnosis of early pancreatic cancer, but they are still in the early clinical trial stage or for single These tumor markers have shown some advantages in the diagnosis of early stage pancreatic cancer, but they are still at the stage of early clinical trials or single-center small sample results, which are still far from being widely used in clinical practice. In addition, the development of proteomics and genomics in recent years has shown great promise in exploring markers with higher sensitivity and specificity. Because of its simplicity, non-invasiveness and affordability, abdominal ultrasound is a routine and preferred test for the diagnosis of occupational diseases of the pancreas. ultrasound can detect occupational lesions of the pancreas, dilated biliopancreatic ducts and metastases in the liver. Color Doppler ultrasound is also helpful in detecting vascular invasion of pancreatic cancer. However, for small pancreatic cancers, its accuracy is greatly reduced. Shandra Bipat et al. conducted a Meta-analysis of data from 68 publications involving 7405 patients with pancreatic cancer with preoperative ultrasound examination and found that its sensitivity and specificity for diagnosing pancreatic cancer were 76% and 75%, respectively [16]. This test can be used as a routine screening test for pancreatic cancer in high-risk groups, but it often needs to be supplemented with further tests due to technical limitations and subjectivity of operation. Multi-row spiral CT is still the most commonly used imaging method for pancreatic cancer diagnosis, staging, preoperative resectability assessment and evaluation of treatment outcome, but its diagnostic accuracy for smaller lesions and metastases such as liver and peritoneum is still not high, and pancreatic thin-layer scan + 3D reconstruction can improve its diagnostic efficiency to a certain extent, in addition, CT-guided puncture biopsy can be performed to improve the early diagnosis rate of pancreatic cancer. With the improvement and popularization of fast imaging sequences and other technologies, MRI has made great progress in the diagnosis and staging of pancreatic cancer. MRCP is a safe and non-invasive imaging technique for pancreatic bile ducts, which is better than ERCP in reflecting the whole picture of pancreatic bile ducts, but it cannot completely replace ERCP in the early diagnosis of pancreatic cancer. PET is a functional test, which theoretically can detect the earliest tumors, but it still has certain false-positive and false-negative rates, and it is expensive. It is difficult to promote the use of PET in clinical practice and in the screening of pancreatic cancer in high-risk groups. Ultrasound endoscopy (EUS) emerged in the 1980s, and since then the technology has improved and has been widely used in the diagnosis and treatment of pancreatic diseases in recent years [17], with a very high sensitivity (>90%) in the diagnosis of occupying pancreatic lesions (even early-stage tumors), and can detect lesions that cannot be detected on CT, MRI, or PET [10]. In addition, EUS can also diagnose some precancerous lesions, such as PanIN,IPMN, etc. Therefore, ultrasound endoscopy meets the requirements of early diagnosis of pancreatic cancer and screening of high-risk groups, and is now used as the first-line examination for early diagnosis of pancreatic cancer and screening of high-risk groups, but EUS still has some shortcomings, such as strong dependence on the experience and ability of the operator, local examination, which cannot detect all pancreatic adenocarcinomas and cannot detect distant metastases, and its differential diagnosis of certain benign occupancies and pancreatic cancer is still difficult. For early stage pancreatic cancer with negative ERCP pathology, the diagnostic accuracy of EUS-FNA is 92% and the specificity is 94%, while for patients with negative CT-guided aspiration, its accuracy and specificity are 84% and 90%, respectively. for patients with negative CT-guided puncture were 84% and 90%, respectively [18]. Several clinical studies at home and abroad have confirmed its irreplaceable role in the early diagnosis of pancreatic cancer. However, due to its limitations, EUS is not suitable for all patients. The specificity of EUS in diagnosing early pancreatic cancer can be improved by combining with other examination methods, such as spiral CT, MRI, etc. Each of the above mentioned examination methods has its own advantages and disadvantages. In clinical practice, the most suitable examination method can be selected according to the specific situation, and the combined application of complementary examination methods is advocated to improve the sensitivity and specificity of diagnosis. After the diagnosis of early pancreatic pancreatic cancer or precancerous pancreatic cancer is obtained, the general condition and vascular invasion of the patient should be systematically examined and evaluated, and its resectability should be judged; if it can be resected, surgical treatment by experienced surgeons in a large pancreatic surgery center is recommended to obtain the best therapeutic effect. If the diagnosis of pancreatic cancer cannot be confirmed or excluded, outpatient follow-up should be intensified to monitor changes in the disease. To improve the early diagnosis rate, early surgical treatment, together with radiotherapy, chemotherapy and other comprehensive treatments is the most fundamental way to improve the prognosis of patients. The collaboration of multiple departments, such as surgery, internal medicine, impact medicine and pathology, is an important method to improve the early diagnosis rate of pancreatic cancer. In addition, screening for pancreatic cancer in high-risk groups has been emphasized by scholars at home and abroad, and relevant clinical studies have confirmed its great value in improving the early diagnosis rate of pancreatic cancer, which should be given attention in future clinical practice. In addition, researchers should strengthen relevant basic research and conduct more in-depth studies on the molecular biological mechanisms of pancreatic cancer, genomics and proteomics to improve the early diagnosis of pancreatic cancer. In addition, researchers should strengthen basic research on the molecular biology of pancreatic cancer, genomics and proteomics to improve the early diagnosis of pancreatic cancer.