Early Detection and Post-operative Monitoring of Gastric Cancer

Who May Qualify: 1. Subject age over 18. 2. Subject has stomach discomfort, and seek medical attention at the Gastric Surgery Department of our center. 3. Subject has or will have gastroscopy and/or pathological examination results at this center. 4. Subject must be able to fully understand the willing to sign a consent form form and be able to personally sign it. Who Should NOT Join This Trial: 1. Subject has serious heart, liver, kidney dysfunction, or mental illness. 2. Subject diagnosed previously with any kind of malignant tumor. 3. Subject is known to be infected with HIV or other related diseases (considering interference from the use of immune drugs). 4. Subject is receiving targeted drugs, immunosuppressants, immunomodulators, and biological therapies. 5. Researchers believe that subject is not suitable for enrollment. 6. Subject can not supply sufficient sample to complete this experiment. Always talk to your doctor about whether this trial is right for you.