Post-operative Monitoring of Gastric Cancer

This study is collecting data from patients who have stomach discomfort and are being evaluated or treated at a gastric surgery clinic, to better understand stomach conditions and cancer outcomes after surgery. **You may be eligible if...** - You are 18 or older - You have stomach discomfort and are being seen at the Gastric Surgery Department at the study center - You have or will have a gastroscopy (camera examination of the stomach) or tissue biopsy at this center - You can understand and sign the consent form yourself **You may NOT be eligible if...** - You have serious heart, liver, kidney, or mental health conditions - You have been diagnosed with any other type of cancer previously - You are known to have HIV or related immune conditions - You are taking targeted therapies, immunosuppressants, or biological agents - You cannot provide sufficient samples for the study Talk to your doctor to see if this trial is right for you.