Parts of patients are diagnosed as H. pylori -negative before ER, whereas the specimens become H. pylori-positive after ER, which may have a role in the recurrence of EGC. Our study aims to determine the difference in H. pylori infection rate of EGC patients before and after ER , and discuss the causes leading to the difference, which can provide references for improving the diagnostic accuracy of H. pylori infection and reducing EGC's recurrence rate.

Gastric cancer is the fourth most commonly diagnosed cancer in the world and the second leading cause of cancer-related deaths. Nowadays, endoscopic resection（ER） is widely accepted as the primary treatment for early gastric cancer (EGC) without lymph node metastasis，which includes endoscopic mucosal resection (EMR) and endoscopic submucosal dissection (ESD).However, recurrence rate after endoscopic resection for EGC still achieves 6.7%-14%. However, there is no comparative analysis about H. pylori infection rate before and after ER yet.

Inclusion Criteria:

• high grade dysplasia(HGD) and EGC patients treated by endoscopic resection(including EMR and ESD) in Ren Ji hospital

Exclusion Criteria:

• Suspect of advanced gastric cancer
• Lesions with light grade dysplasia
• History of gastric surgery
• Poor gastrointestinal preparation
• Patients under unsuitable conditions for examination or treatment, such as acute upper gastrointestinal bleeding, noncorrectable coagulopathy, severe systemic disease, etc

patients with early gastric lesions