Inclusion Criteria:
* \*\*Healthy Controls:\*\*
1. Age \> 18 years;
2. Signed informed consent and willingness to participate in the project.
\*\*Gastric Cancer:\*\*
1. Age ≥ 18 years;
2. Performance status (ECOG) score ≤ 1;
3. Histopathologically confirmed gastric adenocarcinoma;
4. No family history of hereditary cancer;
5. No prior anti-tumor treatment;
6. Availability of primary tumor tissue from surgery or biopsy that meets submission requirements;
7. Availability of peripheral blood samples that meet submission requirements;
8. Willingness and ability to sign the informed consent form to participate in the study.
Exclusion Criteria:
* \*\*Healthy Controls:\*\*
1. Individuals at high risk for hereditary colorectal adenocarcinoma, including family members of the following diseases: family history of gastrointestinal tumors, familial adenomatous polyposis (FAP), hereditary nonpolyposis colorectal cancer (HNPCC/LS), and Peutz-Jeghers syndrome (P-J syndrome);
2. History of chronic metabolic or inflammatory diseases that are difficult to control, such as hypertension, diabetes, chronic viral hepatitis, and inflammatory bowel disease;
3. Known history of other malignancies that have progressed or required treatment within the past 5 years, except for skin basal cell carcinoma and squamous cell carcinoma that have been cured;
4. History of oral or intravenous use of broad-spectrum antibiotics and probiotics within the past month;
5. Regular use of immunosuppressive drugs within the past 6 months;
6. Long-term use of other medications that may affect metabolism, such as hormones;
7. Inability or unwillingness to cooperate with follow-up visits and related examinations;
8. Inability to eat normally or requiring medications or enemas for bowel movements;
9. Presence of psychiatric disorders or other severe cardiovascular diseases;
10. Pregnant, breastfeeding, or planning to become pregnant within the next year;
11. Currently participating in an interventional clinical study or receiving study treatment that may influence the patient's treatment decision.
\*\*Gastric Cancer:\*\*
1. Currently participating in an interventional clinical study or receiving study treatment that may influence the patient's treatment decision;
2. Known history of other malignancies that have progressed or required treatment within the past 5 years, except for skin basal cell carcinoma and squamous cell carcinoma that have been cured;
3. History of chronic metabolic or inflammatory diseases that are difficult to control, such as hypertension, diabetes, chronic viral hepatitis, and inflammatory bowel disease;
4. Presence of poorly controlled chronic comorbidities that may affect prognosis;
5. Presence of psychiatric disorders or other severe cardiovascular diseases;
6. Pregnant, breastfeeding, or planning to become pregnant within the next year;
7. Long-term use of medications that may affect metabolism, such as hormones, immunosuppressants, antibiotics, etc.;
8. Any severe and/or uncontrolled medical conditions, as judged by the investigator, that may affect the patient's ability to participate in the study or interfere with study results.
