Stomach cancer can be diagnosed when cancer cells are found during pathological examination of diseased tissues in the stomach. Stomach cancer is a malignant tumor and the causes of the disease are related to poor dietary habits, atrophic gastritis and other factors. To confirm the diagnosis of gastric cancer, gastroscopy is required to extract a small amount of biopsies and then biopsies are sliced and examined pathologically. Once cancer cells are found in the tissue, it indicates that the stomach has been invaded by cancer cells and can be diagnosed as having stomach cancer. In the early stage, the cancer is relatively limited and has not metastasized to other parts of the body, so the disease can be controlled through timely surgery. Once the cancer cells metastasize, it will be more difficult to treat, and in this case, radiotherapy and chemotherapy should be combined to remove the cancer cells in the body.