Without high diagnostic efficacy of endoscopic forceps biopsy (EFB) and with low diagnostic efficacy of narrow band imaging (NBI) in novice endoscopists and endoscopists of community hospitals in China, it is urgent to improve diagnostic efficacy for gastric cancerous lesions.The investigators will conduct a study to develop and validate a diagnostic model based on NBI for early gastric cancerous lesions under endoscopic observation.

Endoscopic forceps biopsy (EFB) is considered the gold standard and most commonly used for histological diagnosis of gastric epithelial neoplasia before proper management.Many studies have shown that there exist considerable discrepancies between EFB and subsequently resected specimens with discrepancy rate of 27.1-44.5%. On the other hand, with low diagnostic efficacy of narrow band imaging (NBI) in novice endoscopists and endoscopists of community hospitals in China, not higher diagnostic accuracy of gastric cancerous lesions could be observed. Here, the investigators will conduct a study to develop and validate a diagnostic model based on narrow band imaging for early gastric cancerous lesions under endoscopic observation, trying to improve overall diagnostic efficacy for gastric cancerous lesions.

Inclusion Criteria:

• Suspected of having a cancerous lesions
• The age of patients is from 40-80 years
• Patients must undergo esophagogastroduodenoscopy

Exclusion Criteria:

• Clinical diagnosis of advanced gastric cancer
• Acute upper gastrointestinal bleeding
• Severe systemic diseases
• Refuse to attend the study