Endoscopy: Intravenous access is prepared before the examination and an intravenous allergy test with sodium fluorescein (2%, 1 ml) is performed. Confocal laser microendoscopy (CEM) is operated similarly to regular endoscopy and is performed by a single person. In this case, it was operated by a physician with extensive experience (>500 cases) in confocal laser microendoscopy. The routine examination was first performed in the ordinary white light endoscopy mode, and after entering the end of the duodenum, 5-10 ml of 10% sodium fluorescein was injected intravenously, and then the confocal laser microendoscopy mode was activated to retract the scope for observation. For each observation site, it can be observed from surface to depth. The images were acquired by foot pedal and stored as digital files. What was seen microscopically: Under ordinary white light endoscopy, a 5.0 cm × 4.0 cm sized mucosal elevated lesion was seen on the lateral side of the greater curvature of the gastric sinus, with a rough and ulcerated surface, interrupted mucosal fold fusion, poorly demarcated from the surrounding tissue, and easily bleeding when touched (e.g., Figure 1). Under confocal laser microendoscopy, the real-time image showed the disappearance of normal gastric hollows and the basic absence of glandular structures, with only scattered heterogeneous cells of varying size and shape and disorganized glandular-like structures. The pathologic image showed an imprinted ring cell morphology, i.e., the cells were filled with mucus that squeezed the nucleus to one side of the cell, giving it a ring-like appearance (Figure 2). The endoscopic images showed similar signs with hyaline cells and black nuclei that were biased to the side of the cells and close to the cell membrane. Many cells were superficially dispersed and arranged in the lamina propria, with an increased distance between the gastric notch and the gland. Targeted biopsy: Because the confocal laser microendoscope works in close proximity to the microscope window, targeted biopsies can be achieved. In addition to the conventional biopsy, two targeted biopsies were taken at the point where pathological impression cell signs were observed. The material was removed and fixed in 10% formalin solution, paraffin blocks were embedded and sent for routine staining with hematoxylin-eosin (HE, Figure 3) and special staining with Alisin blue-periodic acid Schiff (AB/PAS, Figure 4). The diagnosis was made by 2 experienced pathologists. Gastric indolent cell carcinoma mostly progresses rapidly and has a high degree of infiltration, and is a malignant gastrointestinal tumor that is not easily detected and diagnosed at an early stage. The direct signs and targeted biopsies observed under confocal laser microendoscopy are very beneficial to the early diagnosis of Indocellular carcinoma and help to formulate effective treatment measures. The application of confocal laser microendoscopy in our clinical practice has successfully diagnosed a number of cases of gastric IMC, showing that confocal laser microendoscopy has high practical value in the diagnosis of gastric IMC. Since its introduction in 2006, confocal laser microendoscopy has been widely used in clinical practice, followed by the introduction of the device in several domestic hospitals. It is easy to operate, with clear images and digital storage for systematic analysis. Several studies have shown that confocal laser microendoscopy is suitable for a variety of diseases of the gastrointestinal tract, especially for the diagnosis and monitoring of early tumors and precancerous lesions of the gastrointestinal tract, such as Barrett’s esophagus, gastroesophageal reflux disease, gastric intraepithelial neoplasia, Helicobacter pylori infection, colon polyps, ulcerative colitis and early gastrointestinal tumors, etc. It has a high degree of diagnostic specificity and sensitivity. Confocal laser microendoscopy is a confocal laser microscope integrated into the head end of a conventional electronic endoscope, and its basic structure is based on that of a regular endoscope. The advantage is the in vivo histological simulation of the mucosal layer under the endoscope, direct observation of the cellular structure, 1000x magnification and 250μm scanning depth, high resolution images, comparable to the pathological results of biopsy, commonly known as “optical biopsy”. Compared with traditional biopsy histological examination, it has the following advantages: rapid, non-invasive, multi-point biopsy; guiding targeted biopsy, improving clinical diagnosis rate; allowing the most rapid and optimal diagnosis and timely treatment in real time, avoiding repeated endoscopy. Indolent cell carcinoma is a type of pathological classification (WHO classification) of gastric cancer. It is mainly an adenocarcinoma composed of isolated or small clusters containing intracellular mucinous malignant cells. It has a high degree of malignancy and is mostly found in the middle to late stages with a low 5-year survival rate. Pathological AB/PAS special staining has a high diagnostic rate in identifying indolent cell carcinoma.