In this study, the investigators will prospectively recruit 100,000 individuals, including gastric cancer patients who have not undergone any anti-tumor treatment and non-gastric cancer participants. The investigators will construct a diagnostic model for malignant tumors based on the combination of tongue imaging, tongue coating, saliva, gastric juice, and fecal multi-omics data (including metagenomics, proteomics, metabolomics, etc.). Additionally, the study will explore the relationship between oral, gastric, and intestinal microbiota and the development of malignant tumors.

Patients with gastric cancer were recruited through outpatient clinics, endoscopy units, and inpatient departments of various centers, with all patients requiring a histopathological diagnosis. Non-gastric cancer participants were sourced from community health check-ups, outpatient clinics, and endoscopy units affiliated with these centers.

Inclusion Criteria for Gastric Cancer Patients:

• 18≤age≤90
• Histologically or cytologically confirmed gastric cancer
• No prior chemotherapy, radiotherapy, biotherapy, immunotherapy or other anti-tumor treatment for gastric cancer
• Subject volunteers to join the study, Signs informed consent, has good compliance and can cooperate with follow-up

Exclusion Criteria for Gastric Cancer Patients:

• Two or more kinds of malignant tumors at the same time
• Gastric cancer that has been treated by chemotherapy, radiotherapy, biotherapy, immunotherapy or other anti-tumor therapy
• The use of glucocorticoids and antibiotics in the past three months
• History of long-term medication
• Presence of oral diseases such as tooth and gum diseases
• Subjects who had other factors that might force them to terminate the research ahead of time, such as the development of other severe disease (including mental disease) that required combined treatment, seriously abnormal laboratory examination value, and family or social factors that might affect the subject safety or experimental data collection, as judged by the researchers

Inclusion Criteria for Healthy Participants:

• 18≤age≤90
• Willingness to participate in the study, signing an informed consent form, and demonstrating good compliance

Exclusion Criteria for Healthy Participants:

• History of malignant tumors
• The use of glucocorticoids and antibiotics in the past three months
• History of long-term medication
• Presence of oral diseases such as tooth and gum diseases
• Subjects who had other factors that might force them to terminate the research ahead of time, such as the development of other severe disease (including mental disease) that required combined treatment, seriously abnormal laboratory examination value, and family or social factors that might affect the subject safety or experimental data collection, as judged by the researchers

Histologically or cytologically confirmed gastric cancer, and no prior chemotherapy, radiotherapy, biotherapy, immunotherapy or other anti-tumor treatment for malignant tumor. Gastric cancer patients and healthy participants should not have the following conditions: the use of glucocorticoids and antibiotics in the past three months, a history of long-term medication, as well as oral diseases such as tooth and gum diseases.

We currently have no plans to share individual participant data (IPD) with other researchers.