This is a prospective multicenter comparative study, aiming to compare probe-based confocal laser endomicroscopy (pCLE) and endoscopic biopsies in the diagnosis of the whole specific gastric lesion especially for distinguishing low grade intraepithelial neoplasia (LGIN) from high grade intraepithelial neoplasia (HGIN) and create an endoscopic image database for the follow-up research.

Traditional endoscopic biopsies can only obtain limited tissues from the whole lesion and is invasive, while probe-based confocal laser endomicroscopy (pCLE) can obtain images at a cellular level of the entire lesion area in real time and non-invasively. There were only single-center and small-sample previous researches for comparing the diagnostic accuracy of CLE and traditional biopsy in the entire gastric lesions, and they did not distinguish gastric low grade intraepithelial neoplasia (LGIN) from high grade intraepithelial neoplasia (HGIN). Thus, this study aims to further verify whether pCLE or pCLE combined with biopsy can improve the diagnostic accuracy of the overall lesion and reduce the histological upstaging rate of gastric LGIN after endoscopic submucosal dissection (ESD) by using large sample data and a new pCLE classification method, so as to achieve better guidance of clinical treatment. While verifying the diagnostic efficacy of pCLE, the data of the participants will be collected and collated, and an endoscopic image database will be constructed for the follow-up research.

Inclusion Criteria:

• Over 18 years old and under 75 years old;
• Patients with pathological diagnosis of LGIN, HGIN or early gastric cancer after conventional endoscopy biopsy, whose lesion has clear boundaries under endoscopic observation and is to be admitted for ESD surgery;
• Patients who meet the indications for endoscopic resection of early gastric cancer, or LGIN patients who intend to undergo ESD surgery;
• Patients who are able to provide pathological specimens/sections of previous endoscopic biopsy (in principle, it should be a case of this center).

Exclusion Criteria:

• Patients with advanced gastric cancer or previous gastrectomy;
• Patients with severe cardiopulmonary dysfunction, liver cirrhosis, renal dysfunction, acute gastrointestinal bleeding, esophageal-gastro varices, and coagulation disorders;
• Patients who have a positive result in the fluorescein sodium allergy test;
• Pregnant and lactating women;
• Patients who have psychiatric disorders and are unable to cooperate with endoscopy or sign informed consent.