The occurrence of gastric cancer is associated with standard of living and is more common in developing countries. Risk factors include dietary habits, smoking and H. pylori infection. In fact, there are many examples of viral bacterial and other pathogenic infections causing tumorigenesis in humans, such as eb virus and nasopharyngeal lymphoma, hpv and cervical cancer, hbv and liver cancer, etc. H. pylori causing gastric cancer may be related to long-term chronic gastritis and then progressing to atrophic gastritis and then abnormal epithelial metaplasia precancerous lesions. Commonly used tumor markers include ca724, ca199 and pepsinogen pg. ca724 has a slightly higher sensitivity and slightly lower specificity. Most mildly positive patients with gastroscopic pathology are confirmed to have general chronic gastritis, but they should be alerted if they are much higher than the reference range. The sensitivity and specificity of ca199 is similar to that of ca724 and may be improved with the combination of ca724. ca199 is more affected by cholestasis and can be ruled out with mrcp, in addition to gallstone disease chronic pancreatitis uremic syndrome and even diabetic patients may be mildly elevated. In addition, it is also significantly increased in colorectal cancer pancreatic cancer. PG, reflecting the secretory function of gastric glands, patients with gastric cancer are prone to a decrease in PG1 (decrease in gastric fundic secretion of protease) and a relative increase in PG2 (increase in gastric glandular secretion of mucus), which in turn leads to a decrease in PG1/PG2 ratio.