Objective:To investigate the clinical, endoscopic and pathological features, and treatment and prognosis of gastric adenocarcinoma of fundic gland type of chief cell predominant type (GA-FG-CCP).Methods:Data of 40 GA-FG-CCP patients with 41 lesions diagnosed by histopathology at Ningbo Medical Center Lihuili Hospital and Shanghai East Hospital from January 2018 to May 2023 were collected. Their clinical and endoscopic features, pathological features, immunohistochemical results, endoscopic treatment, and prognosis were analyzed.Results:Among the 40 GA-FG-CCP patients, there were 15 males and 25 females, and the mean age was 60.03 years. Most of them had no obvious clinical symptoms or family history of tumor. Except one case, others had no helicobacter pylori infection. The endoscopic features of white light observation were: ① the main location was the upper part of the gastric body (63.41%, 26/41); ② faded or whitish mucosal surface (56.10%, 23/41); ③ dilated vessels with branch architecture (78.05%, 32/41); ④ no background mucosal atrophy (100.00%, 41/41). The features of magnifying endoscopy with narrow band imaging (ME-NBI) were: ① no obvious demarcation line (85.37%, 35/41); ② enlargement of the crypt opening (87.80%, 36/41); ③ widening of the intervening part (92.68%, 38/41); ④ lack of irregular microvascular pattern (95.12%, 39/41). All patients were confirmed gastric adenocarcinoma of the fundic gland by biopsy. The glands showed a low degree of dysplasia, similar to the differentiation of chief cell predominant pattern, also with scattered parietal cells, forming irregular and anastomosing cords. In the 40 patients, 20 did not receive endoscopic therapy. Twelve out of 21 lesions in 20 cases treated with endoscopic resection infiltrated into the submucosa (20-520 μm), 9 cases were intramucosal carcinoma. There was no lymphatic or venous infiltration, and horizontal and vertical margins were negative. Immunohistochemical staining results showed that the tumor was postive for pepsinogen-Ⅰ and MUC 6, with scattered postive for H +-K +-ATPase, but negative for MUC5AC, MUC2 and CD10, and the Ki-67 labeling index was low. No patients had recurrence or metastasis during mean follow-up of 15.85 months. Conclusion:GA-FG-CCP is rare and very well differentiated. Its clinical symptoms are not obvious, but there is endoscopic characteristics. The detection rate of GA-FG-CCP can be improved by white light and ME-NBI, and the diagnosis can be confirmed by pathology and immunohistochemical staining.