This study aims to test the hypothesis that the diagnosis for histological type, histological grade, LAUREN type, HER-2 expression, MSI/dMMR status, and EBV status in gastric cancer is at least as reliable when performed on endoscopic biopsy specimens as on surgical resection specimens.

Most institutions currently diagnose gastric cancer on endoscopic biopsy specimens but use surgical resection specimens for histological type, histological grade, LAUREN type, HER-2 expression, MSI/dMMR status and EBV status testing. However, gastric cancers treated with neoadjuvant chemoradiotherapy/chemotherapy may undergo a complete pathological response (pCR), with no residual tumors available for testing, and neoadjuvant chemoradiotherapy/chemotherapy may alter the HER-2 expression, MSI/dMMR status and EBV status of the gastric cancer in some instances. Importantly, testing histological type, histological grade, LAUREN type, HER-2 expression, MSI/dMMR status and EBV status of gastric cancer on endoscopic biopsy material could be initiated preoperatively, allowing resultant genetic information to be used in consultation with the patient to inform treatment decisions. Therefore, the preoperative endoscopic biopsy may be a source of suitable and reliable testing material. This study aims to investigate the correlation between histological type, histological grade, LAUREN type, HER-2 expression, MSI/dMMR status, and EBV status in preoperative endoscopic biopsy specimens and their corresponding surgical resection specimens and ascertain whether endoscopic biopsy specimen is a valid and reliable testing material for determining the histological type, histological grade, LAUREN type, HER-2 expression, MSI/dMMR status and EBV status of gastric cancer.

Inclusion Criteria:

1. Lower age limit of research subjects 18 years old and upper age limit of 75 years old.
2. Histologically proven primary gastric adenocarcinoma (Diagnostic biopsies must be collected within 12 months prior to enrollment).
3. Written informed consent from the patient.
4. Patients planned for radical R0 gastrectomy.

Exclusion Criteria:

1. Female in pregnancy or lactation.
2. Patients with gastric cancer who can not undergo tumor resection
3. Suffering from other serious diseases, including cardiovascular, respiratory, kidney, or liver disease, complicated by poorly controlled hypertension, diabetes, mental disorders or diseases.
4. Patients with poor compliance or considered to be poor compliance.
5. Patients received any anticancer drugs, biotherapy, radiotherapy or immunotherapy within 4 weeks before or after enrollment.
6. Patients after organ transplantation, long-term need to take immunosuppressants, autoimmune diseases.

Treatment-naive gastric cancer patients