Gastric cancer is one of the most common malignant tumors, ranking fourth in the number of newly diagnosed cancer cases and second in the cancer death rate each year. In this article, we summarize the prevalence and causes of gastric cancer, and hope to help candidates. Prevalent sites of gastric cancer The vulnerable sites of gastric cancer are sinus (58%), cardia (20%), gastric body (15%), and the whole or most of the stomach (7%). According to the extent of cancer invasion into the stomach wall, it can be divided into early stage and progressive stage gastric cancer. Early stage gastric cancer refers to cancer tissue infiltration depth not exceeding the submucosa layer, regardless of whether it has local lymph node metastasis. Progressive gastric cancer is considered as intermediate stage if the depth of the cancer exceeds the submucosa layer and has invaded the muscle layer, and advanced gastric cancer is called advanced gastric cancer if it invades the plasma membrane or plasma membrane. Etiology The occurrence of gastric cancer is a multifactorial process with multi-step progressive development. 1.Environmental and dietary factors Long-term consumption of moldy food, salted vegetables, smoked and rouged fish and meat, as well as high-salt food can increase the risk of stomach cancer. Smoked and rouged foods contain high concentration of nitrate, which can be formed into nitrite in the stomach by the action of bacterial nitrate reductase, and then combined with amine to form carcinogenic nitrosamines. 2.H. pylori infection The chronic inflammation caused by H. pylori may become an endogenous mutagen; H. pylori is a nitrate reducer, which has the role of catalytic nitrosation and carcinogenic effect; some products of H. pylori promote epithelial cell mutation. 3, genetic factors Gastric cancer has an obvious tendency to gather in families, especially infiltrative gastric cancer has a higher tendency to develop in families, suggesting that the type is related to genetic factors. It is generally believed that the genetic quality makes cancerous substances more likely to cause cancer to susceptible people.