Gastric cancer was once the second most common malignant tumor after lung cancer, but in recent years its incidence has been generally declining worldwide and now ranks as the fourth most common tumor after lung cancer, breast cancer, and colorectal cancer, with 42% of the cases occurring in China. According to WHO statistics, until 2005, stomach cancer was still the first tumor in China in terms of cancer incidence and death. How to reduce the incidence of gastric cancer and improve the early diagnosis rate of gastric cancer has become an urgent clinical problem. Gastric cancer is clinically classified into early gastric cancer (EGC) and advanced gastric cancer (AGC) according to the depth of tumor infiltration. The Japanese Endoscopy Association proposed that according to the depth of tumor infiltration, those who are limited to the mucosa and submucosa but not to the muscle layer, regardless of the size of the tumor, with or without lymph node metastasis, are defined as early gastric cancer, and EGC is further divided into mucosal cancer (MC) and submucosal cancer (SM). Improving the diagnosis rate of EGC, achieving early detection and early treatment are the key factors to improve the survival rate of gastric cancer patients. With the popularization of endoscopy technology and the enhancement of people’s health care awareness, the early diagnosis and early treatment of gastric cancer have been greatly improved, and the detection rate of EGC can even reach 63.04% when regular gastroscopy is performed for some special groups. With the gradual research on EGC, especially the research on the law of lymph node metastasis and the characteristics of biological behavior, the surgical methods or treatment concepts of EGC have also emerged on the basis of traditional D2 radical surgery, such as reduction surgery or laparoscopic surgery with the purpose of improving patients’ postoperative quality of life by appropriately reducing the scope of gastrectomy and lymph node dissection, as well as endoscopic minimally invasive treatment. Japan is the country with the highest diagnosis rate of early gastric cancer, accounting for more than 50% of all gastric cancers; Korea is slightly lower, but also reaches 40%-50%; Europe and the United States is 10%-20%; the diagnosis rate of EGC in China is still low, and the overall average level hovers around 10%; the diagnosis rate of EGC in domestic hospitals is highest in Ruijin Hospital affiliated to Shanghai Jiaotong University School of Medicine. The highest EGC rate among domestic hospitals was reported by Ruijin Hospital of Shanghai Jiaotong University School of Medicine, which accounted for 21.8% of all gastric cancers in 2007. Zhongshan Hospital of Fudan University reported in 2009 that its EGC accounted for 15.03% of the total number of surgically treated gastric cancers in the same period; Renji Hospital of Shanghai Jiaotong University School of Medicine reported 248 cases of EGC in the past five years from January 2003 to September 2008, accounting for 14.2% of the total number of surgically treated gastric cancers in the same period, which are higher than the overall average level in China. Given the strength of the endoscopy centers of the above hospitals and the rich experience of the doctors coupled with the good examination equipment, the overall early diagnosis rate of gastric cancer is relatively high, but even so, the diagnosis rate of EGC in many general hospitals in economically developed areas such as Shanghai, Beijing and Guangzhou is still quite different from that in Japan and Korea. At present, the most widely used endoscope for the diagnosis of EGC is the general electronic endoscope, which allows multiple people to dynamically observe the microscopic image of the stomach through a TV screen by installing a small TV camera. The advantage is that the change of hue can be observed, and some gastric cancers that are difficult to detect during barium X-ray meal can be captured by slightly reddened or faded lesions seen during endoscopy; on the other hand, if the lesion is well-defined, a clear boundary can be observed and excised under endoscopy; in addition, the ability to perform biopsy is the biggest advantage of endoscopy, which can directly determine the benignity and malignancy of the lesion, so its position in In addition, the ability to perform biopsy is the greatest advantage of endoscopy, which can directly determine the benignity and malignancy of lesions, so its position in clinical examination is extremely important. In recent years, with the rapid development of endoscopic equipment and technology, new endoscopic methods, including ultrasound endoscopy, magnification endoscopy, pigmented endoscopy, fluorescence endoscopy, and confocal laser microscopy, have been gradually applied in clinical practice. Ultrasound endoscopy is a new examination method that integrates endoscopic technology and ultrasound technology, by attaching an ultrasound probe to the endoscope to assist in diagnosing the depth of tumor infiltration and the presence of lymph node metastasis. By comparing the diagnostic value of general endoscopy, abdominal CT and ultrasound endoscopy for EGC tumor size and lymph node infiltration, it was found that the positive predictive value of ultrasound endoscopy for EGC was 94.1%, which was better than the first two methods; and it was 92.6% in determining adjacent lymph node metastasis, which was also higher than the 90.1% of abdominal CT. However, in China, only a small percentage of patients with EGC diagnosed by general endoscopy then undergo ultrasound endoscopy due to cost and tolerability issues, so the clinical application of ultrasound endoscopy is also limited. The purpose of magnifying endoscopy for EGC is mainly to determine the benignity and malignancy of the lesion, distinguish its histological type as well as to judge the depth and breadth of infiltration of malignant lesions, which can improve the purpose of biopsy, avoid unnecessary biopsy trauma, and facilitate the early diagnosis and treatment of gastric cancer. The use of pigmented endoscopy is to spread or spray various pigments on the mucosal surface of the digestive tract, which can more easily capture the subtle bump and hue changes of the mucosa, and further use the relationship between the mucosa and the hue to be able to observe lesions that are difficult to be observed by ordinary endoscopy.Mouzyka et al. reported that the use of pigmented endoscopy can significantly improve the detection rate of gastric cancer, and its sensitivity and specificity for gastric adenoma and adenocarcinoma, using pathology as the gold standard The sensitivity and specificity reached 92.9% and 82.3% for gastric adenoma and adenocarcinoma, respectively. Chromatography endoscopy has advantages in the detection of gastric precancerous lesions and early microcarcinomas. Fluorescence endoscopy is an optical diagnostic technique that has been actively researched in recent years, mainly using the differences in laser-induced autofluorescence spectra of tissues, and was reported by Kato et al. to be more sensitive than conventional endoscopy in the detection of superficial gastric tumors, but its specificity was not strong (40% vs. 80%), and its clinical application is still limited. Confocal microendoscopy can perform confocal microscopy for the purpose of optical biopsy. Through the observation of normal gastric mucosa and EGC, confocal endoscopy can predict the histological type of EGC based on the change of microvasculature. Differentiated gastric cancer tissues have significantly more mucosal vessels with irregular arrangement of varying thickness of tubular diameter, while undifferentiated gastric cancer has significantly fewer microvasculature and irregular short branches, which can be used for the diagnosis of EGC. The continuous progress and improvement of these endoscopic examinations are aimed at improving the detection rate of EGC and the early diagnosis of gastric cancer, thus improving the overall therapeutic efficacy of gastric cancer. With the development of modern imaging, CT examination has been widely used in the preoperative evaluation of gastric cancer. From the early single-row CT to today’s multi-row spiral CT (MSCT), which includes thin layer scanning, Multiplanar reconstruction (MPR), and various images such as simulated endoscopy, gas casting, and simulated lumen obtained through computer workstations. Due to the small size of EGC, the value of judging the thickness of the gastric wall alone is limited. With the help of 64-row MSCT with layer thickness up to 12.5 px and combined with multi-phase enhancement of the difference between the enhancement of the cancer and the normal gastric wall, the detection of the lesion is facilitated. The accuracy of EGC localization diagnosis was greatly improved by the use of MPR technique, which can observe the suspected lesion location from different directions such as coronal and sagittal planes. 77% of the diagnostic accuracy of EGC was achieved by Kim et al. using 64-row MSCT, and the accuracy of EGC diagnosis was increased to 94.1% by Shimizu et al. in combination with MPR technique. Meanwhile, CT angiography can accurately evaluate the perigastric blood supply arteries preoperatively and can detect vascular variants, providing comprehensive imaging information for the laparoscopic surgery currently performed for EGC, which is of greater significance for safe and rapid laparoscopic surgery. Our experience in Renji Hospital shows that gastric MSCT is important for determining the site and nature of tumor and providing surgical plan, and it has obvious advantages over general gastroscopy and X-ray barium enema in preoperative localization and diagnosis of tumor, whether there is adjacent organ invasion and lymph node metastasis, etc. However, it is suggested that MSCT can be used as a complementary examination to gastroscopy because it cannot directly perform pathological biopsy. Therefore, MSCT is recommended as a supplementary examination to gastroscopy. Evolution of surgical approach and treatment concept of early gastric cancer Traditional EGC surgery has been performed with radical D2 lymph node dissection as the basic guideline, but after the gradual study of EGC, it was found that the obvious difference of EGC compared with progressive gastric cancer is the low rate of lymph node metastasis, thus changing the previous concept that all EGC must be performed with D2 lymph node dissection. In contrast, for patients with EGC without lymph node metastasis, indiscriminate lymph node dissection may instead increase surgical trauma and increase surgical complications. Meanwhile, conditions such as bile reflux esophagitis and gastritis that arise after conventional major gastrectomy may also reduce the postoperative quality of life of EGC patients. Therefore, on the premise of ensuring the radicality of EGC surgery, the postoperative quality of life of patients should be improved as much as possible, and the incidence of surgical trauma and postoperative complications should be reduced. In recent years, there is a trend of narrowing the scope of surgery for patients with early gastric cancer, and a variety of minimally invasive or reduced surgery (Less invasive surgery) has emerged, such as EMR, ESD, laparoscopic gastric wedge resection, gastric segmental resection, pylorus-preserving gastrectomy, etc. In the 1st edition of “Guidelines for the Treatment of Gastric Cancer” published by the Japan Gastric Cancer Association (JGCA) in 2001, a clear concept of reduction surgery for EGC was introduced and the corresponding surgical indications were formulated, and the so-called reduction surgery refers to the reduction of gastric resection volume and the reduction of lymph node resection area. The reduction of resection volume refers to partial gastrectomy, segmental gastrectomy and pylorus-preserving gastrectomy, etc. The reduction of lymph node resection area refers to modified radical surgery A (D1+α, α=No.7, No.8a added for lower gastric cancer) and modified radical surgery B (D1+β, β=No.7, 8a, 9) for EGC. The guidelines state that the suitability of EGC for reduction surgery depends on the preoperative and intraoperative diagnosis. Our experience suggests that for EGC patients, the choice of individualized surgical plan should be focused on: that is, the size and location of the lesion and the lymph node metastasis should be evaluated preoperatively by means of ultrasound endoscopy and gastric MSCT, and different surgical approaches should be selected according to the evaluation. The 3rd edition of the Guidelines for the Treatment of Gastric Cancer, developed by the JGCA and used since January 1, 2010, abolished the anatomical N-staging (classification of lymph node stations) method long used in Japan and replaced it with an N-staging method based on the number of lymph node metastases, with a fixed lymph node clearance range according to the procedure and a more concise D1/D2 clearance range for lymph node clearance. In the new version of gastric cancer treatment guidelines, No.7 is designated as D1 clearance scope treatment, so the indications for D1 clearance surgery include: intra-mucosal carcinoma that cannot undergo EMR and differentiated deep submucosal carcinoma without lymph node metastasis and carcinoma foci ≤37.5px. And the indications for D1+No.8a+No.9 clearance include T1 tumors except for the above cases. With the development of minimally invasive treatment, endoscopic and laparoscopic EGC has been widely performed in Japan and Korea, and also achieved good long-term and near-term outcomes. Endoscopic mucosal resection (EMR) can maximize the preservation of gastric tissue and improve the quality of life of patients. In Japan and Korea, it has become one of the treatment methods for EGC. Kim et al. showed that 506 cases of EGC underwent EMR in 13 centers in Korea, with a complete resection rate of 77.6% and a local recurrence rate of 6%. Kojima et al. (21) reported that 1832 Japanese patients with EGC underwent EMR: the complete resection rate was 73.9%, and the complication rate was 1.9% (of which 1.4% was bleeding and 0.5% was perforation). In recent years, the development of endoscopic submucosal dissection (ESD) has significantly broadened the scope of gastroscopic treatment, which was included as a standard treatment in the 2nd edition of the guidelines. In the 3rd edition of the guidelines, the indications for ESD were further clarified: (1) UL(-), differentiated M cancer; (2) carcinoma, UL(+), differentiated M cancer; (3) UL(-), carcinoma <50 px, undifferentiated M cancer; (4) carcinoma <75 px, differentiated SM1 cancer. resection rate was 93%) and the gastric perforation rate was 6.1% (all treated endoscopically), and no recurrent cases were found at 1 year follow-up. So far, we have also carried out more than 80 cases of minimally invasive treatment for EMR and ESD. Although some patients have experienced complications such as insufficient resection, residual positive tissue at the base, and postoperative bleeding or even perforation, the overall treatment results are still positive, and no recurrence has occurred in the short term. Since both EMR and ESD require better equipment and higher surgical skills, as well as accurate and comprehensive pathological examination, they have not been widely performed in China, and there is still a lack of large number of case reports. In 1994, Kitano et al. in Japan first reported laparoscopic radical distal major gastrectomy for EGC. Since laparoscopic radical gastrectomy can not only achieve complete resection of the primary lesion, but also perform appropriate lymph node dissection, it is gradually being widely used in the surgical treatment of EGC. In recent years, the proportion of radical laparoscopic gastric cancer resection for EGC in Japan and Korea has been increasing year by year, and a multicenter retrospective study by Kitano et al. reported 1294 patients with radical laparoscopic gastric cancer from 1994 to 2003. Lee et al. compared 106 radical laparoscopic gastric cancer resections with 105 open distal gastrectomies for EGC during the same period, and there was a significant difference in postoperative complication rates (4.7% and 13.3%, P=0.046), while there was no significant difference in the 5-year postoperative survival rate (95.9% and 94.9%, respectively). We compared more than 60 EGC patients who underwent LADG with those who underwent open surgery in the same period in Renji Surgery in the past 3 years and found that the former had the advantages of less surgical trauma, fewer postoperative complications, shorter hospital stay, and high postoperative quality of life with good recent results. Since the number of cases is still small, we need to increase the number of surgical cases and further compare the long-term efficacy, but we have already seen the good prospect of laparoscopic radical gastric cancer surgery in EGC treatment. With the gradual development of evidence-based medicine to guide clinical surgical practice and the use of various advanced diagnostic tools and the continuous updating of surgical instruments and equipment, it is the most urgent task for Chinese gastroenterologic surgeons to develop a standardized treatment for EGC with Chinese characteristics based on further understanding of the characteristics of EGC. Only with standardized treatment can the development of gastrointestinal surgery be promoted and the diagnosis and treatment level of gastric cancer in China be truly improved.