Pathological biopsy before endoscopic submucosal dissection (ESD) the gastric lesion plays an important role in differentiating the pathological nature of the lesion and guiding treatment decisions. However, due to the influence of the materials used, the sensitivity of pathological biopsy is not satisfactory. Confocal Laser Endomicroscopy (CLE) is a technology that integrates a confocal microscope into an endoscope. It enables the acquisition of high-resolution microscopic images of the mucosal layer in real-time (with a magnification of up to 1000 times), and it is an optical biopsy technique. It has unique value in the determination of the pathological nature of gastric lesions. The main purpose of this study is to compare the sensitivity of pathological biopsy and CLE in differentiating the pathological nature of gastric lesions.

Inclusion Criteria:

• patients aged 18 to 85 years who were scheduled for endoscopic submucosal dissection due to early-stage gastric cancer were consecutively enrolled.

Exclusion Criteria:

• Severe cardiac or pulmonary dysfunction, impaired renal function, coagulopathy, pregnancy or lactation, allergy to fluorescein, and inability to provide informed consent.

The absolute indications for curative endoscopic resection (ESD) include moderately and well-differentiated, nonulcerated, mucosal lesions that are ≤2 cm in size. Other relative (expanded) indications for gastric endoscopic submucosal dissection include moderately and well-differentiated superficial cancers that are >2 cm, lesions ≤3 cm with ulceration or that contain early submucosal invasion, and poorly differentiated superficial cancers ≤2 cm in size.