Gastric cancer is one of the most common malignant tumors, with the highest incidence and mortality rate among gastrointestinal tumors. The traditional typing is based on morphological structure and cellular histological characteristics. Gastric cancers of different tissue types have different morphological structures and biological behaviors, as well as different epidemiological and molecular mechanisms. With the development of modern molecular biology technology, biology and pathology are interpenetrating each other, and the connection between them is getting closer and closer, gradually forming a new pattern based on traditional pathological morphological methods and molecular biology features as the research hotspots. I. Pathological typing of gastric cancer 1. Commonly used typing: There are many existing pathological typing systems of gastric cancer, and the commonly used ones are histomorphological typing, such as Borrmann typing, WHO typing and Lauren typing. 1.1, Borrmann typing A typing method proposed by German pathologist Borrmann in 1926, mainly based on the morphological characteristics of tumor on the mucosal surface and the ratio of exogenous to endogenous, gastric cancer is divided into 4 types: Type I (nodular type), tumor grows into the lumen and is polyp-like, with a wide base and clear boundaries, ulcers are rare, but there may be small erosions. This type is the least common. Type II (ulcerated limited type), the tumor has a large ulcer formation, the edge is elevated obviously, the boundary is clear, the infiltration to the surrounding is not obvious. Type III (infiltrating ulcer type), the tumor has obvious ulcer formation, the edge is partly elevated, partly destroyed by infiltration, the boundary is unclear, the surrounding infiltration is more obvious, the scope of cancer tissue infiltration in the submucosa exceeds the tumor boundary seen by the naked eye, it is the most common type. Borrmann staging is the classic staging method of gastric cancer, which is still widely used internationally. 1.2, Lauren’s staging In 1965, Lauren divided gastric cancer into intestinal type and diffuse type according to the tissue structure and biological behavior of gastric cancer. Intestinal type gastric cancer originates from intestinal mucosa, generally has obvious glandular structure, tumor cells are columnar or rectangular, brush-like edge is visible, tumor cells secrete acidic mucus substance, similar to the structure of intestinal cancer; often accompanied by atrophic gastritis and intestinal metaplasia, mostly seen in elderly men, with longer course, higher incidence and better prognosis. Diffuse type of gastric cancer originates from the intrinsic mucosa of the stomach; the cancer cells are poorly differentiated, grow diffusely, lack cellular junctions, and generally do not form glandular ducts; many hypofractionated adenocarcinomas and indolent cell carcinomas belong to this type; mostly seen in young women, prone to lymph node metastasis and distant metastasis, and have a poor prognosis. henson et al. In the United States, the incidence of intestinal gastric cancer showed a decreasing trend among American men, women, African-Americans and whites, while diffuse gastric cancer showed an increasing trend among the same population, with the incidence rate increasing from 0.3/100,000 in 1978 to 1.8/100,000 in 2000, with the most pronounced increase in the incidence of indolent cell carcinoma. The Lauren typing reflects not only the biological behavior of the tumor, but also its etiology, pathogenesis and epidemiological features. Lauren typing is concise and effective, and is often used in Western countries. However, 10% to 20% of cases have both intestinal and diffuse features, which are difficult to be classified as either one of them, thus called mixed type. 1.3, WHO staging WHO proposed an international staging system based on tissue origin and its heterogeneity in 1979. This system classifies gastric cancer into adenocarcinoma, adenosquamous carcinoma, squamous cell carcinoma, carcinoid carcinoma, undifferentiated carcinoma and carcinoma that cannot be classified. When two types of tissues coexist, they are typed according to the predominant tissue type, while the secondary tissue type is indicated. Adenocarcinoma is also classified according to histological characteristics: papillary adenocarcinoma, tubular adenocarcinoma, mucinous adenocarcinoma, and indolent cell carcinoma; and according to the degree of differentiation (the least differentiated part): highly differentiated, moderately differentiated, and poorly differentiated adenocarcinoma. 1990 WHO revised the histological staging of gastric cancer, and the new criteria divided gastric cancer into two categories: epithelial tumors and carcinoid tumors. tubular adenocarcinoma, hypofractionated adenocarcinoma, mucinous adenocarcinoma, and indolent cell carcinoma), squamous adenocarcinoma, undifferentiated carcinoma, and carcinoma that cannot be classified. Gastrointestinal carcinoid tumors are slow-growing, complex neuroendocrine tumors, and the new WHO diagnostic criteria of 2000 classify carcinomas as benign or malignant according to their differentiation, tumor size, depth of infiltration, vascular invasion, and metastasis. Malignant carcinoid tumors have moderate or higher heterogeneity, increased nuclear index (>2/10 HPF) or tumor diameter >1 cm or tumor invasion into the intestinal wall (intramural or extra-muscular) or lymph node or liver metastasis. Benign carcinoid tumor cells have characteristics such as moderate or below heterogeneity, nuclear division index ≤2/10 HPF, tumor diameter ≤1 cm, and no local infiltration and metastasis. rindi et al. classified gastric carcinoid tumors into type I to type III: type I, with chronic atrophic gastritis; type II, which may be associated with Zhuo-Ai syndrome and multiple endocrine neoplasms (MEN2I); type III, sporadic gastric carcinoid tumors. 2.Other subtypes 2.1, early gastric cancer The concept of early gastric cancer was introduced by the Japanese Society of Gastrointestinal Endoscopy in 1962, which refers to lesions invading only the mucosa or submucosa, regardless of the size of the cancer and the presence or absence of lymph node metastasis. Correspondingly, gastric cancer with lesions deeper than the submucosa is called progressive gastric cancer. Progressive gastric cancer is then classified according to Borrmann’s staging method, which is also a widely used classification method for gastric cancer in the world. Early gastric cancer is divided into 3 types according to the general morphology: augmented, superficial and indurated; superficial type is the most common and often exists in combination with other types, which are further divided into 3 subtypes: superficial augmented, superficial flat and superficial indurated. In general, the superficial concave type and depressed type are common in Asian countries.