When clinical symptoms such as nausea, vomiting, gastric distension or upper abdominal pain, acid reflux, or hematemesis, as well as melena occur, it is necessary to consider the possibility of gastric cancer and seek timely medical attention. Completing a gastroscopy and obtaining a biopsy under gastroscopy are essential. If cancer cells are found, this is the most important diagnostic method for confirming gastric cancer. After the diagnosis of gastric cancer, further examinations like endoscopic ultrasound and CT scans of the chest and abdomen are required to assess the approximate stage of the patient and to decide the subsequent treatment plan.