Stomach cancer is a malignant tumor that occurs in the stomach. The incidence of gastric cancer in China is highest in northwest China, followed by northeast China and Inner Mongolia, followed by east China and coastal China, and lowest in south-central China and southwest China. Since the etiology of gastric cancer has not been fully elucidated, it is difficult to implement primary prevention against the etiology, but if some precancerous lesions are closely observed and treated clinically, the detection rate of early gastric cancer can be improved. There are two main causes of gastric cancer: environmental factors The occurrence of gastric cancer is mainly related to environmental factors, including soil, water, food and dietary habits, among which dietary factors are the most important. The long-term contact of nitrosamine compounds with gastric mucosa may be related to the occurrence of gastric cancer. Salt curing, smoking and frying can produce polycyclic aromatic hydrocarbon compounds in food, and a representative carcinogen is 3,4-benzopyrene. Moldy foods such as peanuts and corn contain aflatoxin and trichothecene, which can induce liver cancer and stomach cancer. High-salt foods such as pickled fish and salted vegetables are also noted. Although high salt itself is not carcinogenic, it can damage the gastric mucosa and increase the contact between gastric mucosa and carcinogenic agents. The incidence of gastric cancer is lower when people eat more fresh fruits with high vitamin C content because vitamin C has a reducing effect, which can promote the reduction of nitrite to nitrogen oxide and reduce the synthesis of nitrosamines. The incidence of gastric cancer among relatives of patients with gastric cancer is four times higher than that of normal people, suggesting that congenital factors such as genetic genes also have a certain relationship with its development. In recent years, a lot of data have proved that gastric cancer, like most other cancers, rarely occurs directly from the normal gastric mucosa, but often undergoes a long evolutionary stage before the appearance of clinically obvious cancer, and the lesions that appear during this period are called precancerous lesions. Precancerous state refers to clinical conditions or diseases that have a significantly increased risk of developing gastric cancer; precancerous lesions refer to a group of histopathological changes that are prone to cancer, i.e. heterogeneous hyperplasia. The precancerous state of the stomach is mainly: ① benign epithelial polyps. Generally, they can be divided into proliferative polyps and adenomatous polyps. The former is occasionally seen to be malignant, while the latter, especially those with a diameter of 2 cm or more, has a high rate of malignant transformation. ②Chronic atrophic gastritis. (iii) Intestinal metaplasia. Most of the atrophic gastric mucosa has intestinal metaplasia. At the same time, the gastric mucosa with intestinal metaplasia does not necessarily have obvious atrophy, and with age, intestinal metaplasia is also more common, and almost all people over 70 years old have intestinal metaplasia, so intestinal metaplasia and atrophic gastritis are not synonymous. Intestinal metaplasia can be divided into two types: complete and incomplete: complete type has? The complete type has the characteristics of intestinal mucosa, with absorptive cells, cup cells and Parnett’s cells, and is also called small intestine type of intestinal metaplasia; the incomplete type of intestinal metaplasia has poorly differentiated cells, lacks Parnett’s cells, and the mucosal epithelium contains sulfate mucus, and has the characteristics of large intestine mucosa, and is also called large intestine type of intestinal metaplasia. The cells of incomplete intestinal metaplasia are poorly differentiated, and the heterogeneity of the nucleus is more obvious, which is closely related to the occurrence of gastric cancer. ④ Chronic gastric ulcer. It is generally believed that the cancer rate of chronic gastric ulcer is about 0.5-2% if the duration of the disease is more than 5 years. ⑤ Residual stomach. The longer the postoperative interval, the higher the incidence of gastric cancer, which usually occurs more than 10 years after surgery and may be related to bile reflux. (6) Giant gastric mucosal crepitations (Menetrier’s disease). There is clinical hypoproteinemia and swelling, and serum protein is lost through the giant gastric mucosal folds. The cancer rate is 10%. A precancerous lesion of the stomach is a heterogeneous hyperplasia, the birth of which is determined by histopathological sectioning. Gastric mucosal heterogeneous hyperplasia can be divided into three levels: mild cases are not easily distinguishable from inflammatory regenerative changes of gastric mucosa and can often be reversed to normal; moderate cases are benign but are important precancerous lesions and should be followed up regularly and repeated gastroscopy and tissue examination; severe cases are suspected to be cancerous and should be followed up closely in the near future, and if cancer cannot be excluded, surgery is recommended. In terms of symptoms, there is no specific symptom of gastric cancer. The symptoms of common diseases such as gastritis and hepatitis are basically the same as those of gastric cancer, so it is difficult to identify gastric cancer from symptoms. After advanced stage, in addition to the abdominal symptoms, stomach cancer also has wasting, which is a manifestation of malignant tumor. In other words, once the wasting occurs, the disease is in the middle and late stage. It is not easy to identify tumor from symptoms, no matter from which tumor, it is not easy to be detected early. For the early detection of gastric cancer, the international common is gastroscopy. For example, Japan is a high incidence area of gastric cancer, ranking first in the world. Japan is engaged in census, which is conducted once a year for people over 40 years old. The treatment effect of gastric cancer in Japan is much better than that in China, and there are many early gastric cancers. They use gastroscopy for screening, and if a problem is found in a place after gastroscopy, if a piece of tissue as big as a grain of rice is bitten, the pathology report will clearly diagnose if it is gastric cancer. But this is very difficult to do in China. Firstly, people think that gastroscopy is painful, and secondly, the population base of China is so large that census is not achievable in China. What are the main treatment methods for gastric cancer? One is surgery, the other is radiotherapy, and the third is chemotherapy. The fourth method is biological therapy, which is not yet fully accepted by everyone and has to be further discussed. After surgery, chemotherapy plan will be considered according to pathology, staging and metastasis. Radiotherapy for gastric cancer has been done more in the international arena, but less in the domestic arena. Radiotherapy for gastric cancer is still effective from the perspective of international phenomenon, and it has been done less in China. Chemotherapy is routinely done after surgery for middle and late stage gastric cancer. If it is already in the middle or advanced stage when it is found, is it not suitable for surgery? Some of the intermediate stage can be operated, because the advanced stage is distant metastasis, liver metastasis, lung metastasis, and local infiltration is very strong, so chemotherapy is recommended. There is a new term called “neoadjuvant chemotherapy”. At present, clinical tumor stage: stage I, II, III, IV, neoadjuvant chemotherapy is to “downgrade” the clinical stage, such as from stage IV to stage III, stage III to stage II, etc., and then do surgery. Neoadjuvant chemotherapy is to reduce the clinical stage from stage IV to stage III, stage III to stage II, etc., and then perform surgery, and then chemotherapy after surgery, which is better than surgery and then chemotherapy. Can gastric cancer be operated by minimally invasive method? Whether minimally invasive methods can be used depends on two aspects. Firstly, whether the whole stage is early or not, some early stage cancers can be cut off in the stomach through endoscopy without surgery. Second: Minimally invasive is laparoscopy, in which five eyes are made in the stomach with illumination and operation to cut off the lesion. Because the surgical specimen of gastric cancer requires to be taken out intact, a small incision is made and the hand is inserted into the abdominal cavity to remove the specimen – hand-assisted laparoscopic surgery. The purpose is to maintain the integrity of the specimen and perform a complete analysis of the specimen, including: pathological nature, depth of tumor invasion, lymph node metastasis, etc., in order to guide reasonable postoperative adjuvant treatment.