Therefore, patients with symptoms of gastrointestinal alarm (including dysphagia, progressive weight loss, gastrointestinal bleeding and nausea and vomiting) should undergo gastroscopy and multi-site biopsy in time to detect precancerous gastric diseases and early gastric cancer. Chronic atrophic gastritis: It is the most important and common precancerous gastric disease, especially when accompanied with intestinal epithelial hyperplasia and heterotypic hyperplasia. Gastric ulcer: The cancer rate of gastric ulcer is 0.4%-3.2%, and it is still common when combined with chronic atrophic gastritis, intestinal epithelial hyperplasia and heterotypic hyperplasia. 3.Gastric polyps: Gastric polyps are divided into two categories: hyperplastic polyps and adenomatous polyps. Proliferative polyps have a low cancer rate of about 1%; adenomatous polyps have three pathological types: tubular adenomas have a cancer rate of about 10%, villous adenomas also known as papillary adenomas have a cancer rate of 50%-70%, and mixed adenomas are in between. It can be seen that adenomatous polyps should be given sufficient attention, in addition to polyps larger than 2 cm in diameter, broad-based, multiple polyps have a higher cancer rate. 4.Residual stomach: More than 5-10 years after resection surgery for benign gastric disease and more than 20 years after surgery for gastric malignant tumor, cancer belongs to residual stomach cancer, the incidence rate is generally 0.3%-10%. 5.Wart gastritis: also known as pockmarked gastritis, the natural course of the disease is long, some months naturally fade, some last for years. The cancer rate is not yet available statistics. 6.Great gastric mucosal hypertrophy: this disease is rare, and the cancer rate is usually 10%-13%. Pre-cancerous gastric disease is not equal to precancerous lesion, but precancerous gastric disease is a clinical disease with the tendency of malignant change. Precancerous lesions are pathological concepts, also known as atypical hyperplasia or intraepithelial neoplasia. Depending on the degree of heterogeneity and the extent of involvement, they are classified as mild or severe. Mild atypical hyperplasia can be progression-free for many years or even reversible after aggressive treatment, but 75% of severe atypical hyperplasia evolve into cancer within 8 months. Precancerous disease and precancerous lesions can usually be removed endoscopically with good prognosis if they are detected in time.