Gastric carcinoma is a malignant tumor originated from the gastric mucosa epithelium, which ranks the first among various malignant tumors in China. The incidence of gastric carcinoma has obvious regional differences, and the incidence of gastric carcinoma is significantly higher in the northwest and eastern coastal areas of China than in the south. The most common age is over 50 years old, and the ratio of male to female morbidity is 2:1. Gastric cancer tends to be younger due to changes in diet, increased work pressure and helicobacter pylori infection. Gastric cancer can occur in any part of the stomach, more than half of which occur in the gastric antrum, the large curvature of the stomach, small curvature of the stomach and front and rear walls can be involved. The vast majority of gastric cancer belongs to adenocarcinoma, early without obvious symptoms, or the occurrence of upper abdominal discomfort, belch and other non-specific symptoms, often similar to gastritis, gastric ulcer and other chronic gastric disease symptoms, easy to be ignored, therefore, the early diagnosis rate of gastric cancer in China is still low. The prognosis of gastric cancer is related to its pathological stage, site, histological type, biological behavior and therapeutic measures.
1. Regional environment, diet and living factors
The incidence of gastric cancer has obvious regional difference. The incidence of gastric cancer in the northwest and east coastal areas of China is obviously higher than that in the south. The incidence of distal gastric cancer is high in people who eat smoked and salted food for a long time, which is related to the high content of carcinogens or precarcinogens such as nitrite, mycotoxin and polycyclic aromatic compounds in food. Smokers are 50 percent more likely to develop stomach cancer than nonsmokers.
2. Helicobacter pylori (Hp) infection
The adult Hp infection rate in the high incidence area of gastric cancer is above 60%. Helicobacter pylori can cause cancer by converting nitrate into nitrite and nitrosamine. Hp infection causes chronic inflammation of gastric mucosa and environmental pathogenic factors accelerate the excessive proliferation of mucosal epithelial cells, leading to aberrant carcinogenesis. The toxic products of helicobacter pylori, CagA and VacA, may have the effect of promoting cancer, and the detection rate of anti-caga antibody in gastric cancer patients is significantly higher than that in the general population.
3. Precancerous lesions
Gastric diseases include gastric polyps, chronic atrophic gastritis and gastric stump after partial gastrectomy. These lesions may be accompanied by chronic inflammatory processes to varying degrees, intestinal metaplasia or atypical hyperplasia of gastric mucosa, and may be transformed into cancer. Precancerous lesions refer to the gastric mucosal histopathological changes that are prone to canceration, and are the borderline pathological changes in the transformation from benign epithelial tissues to carcinoma. Gastric mucosal epithelial dysplasia is a precancerous lesion, which can be divided into mild, moderate and severe degrees according to the degree of cell dysplasia. Sometimes, it is difficult to distinguish severe dysplasia from well-differentiated early gastric cancer.
Inheritance and genes
Genetic and molecular biology studies have shown that the incidence of gastric cancer in blood relatives of gastric cancer patients is 4 times higher than that in the control group. The canceration of gastric cancer is a multi-factor, multi-step and multi-stage development process, involving the changes of oncogenes, tumor suppressor genes, apoptosis-related genes and transfer-related genes, etc., and the forms of gene changes are also diverse.
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