Abstract
BACKGROUND: Fundic gland tumors are a rare subtype of gastric tumors with fundic gland differentiation. This group of tumors has a low incidence rate and shows indistinctive cellular atypia, obvious structural atypia, special tissue morphology, and clinical prognosis, thus leading to diagnostic challenges. AIM: We aimed to investigate the clinical and endoscopic characteristics and pathological features of gastric adenocarcinoma of the fundic gland (GA-FG) to provide a better understanding of this disease. METHODS: We collected data from patients diagnosed as having GA-FG at Guangdong Provincial People's Hospital between January 2019 and April 2024. The analysis focused on their clinical data, endoscopic characteristics, pathological morphological characteristics, immunohistochemistry results, treatment, and prognosis. RESULTS: Among the four patients were two men and two women (age range, 52-65 years). The tumors were mainly located in the gastric fundus and gastric body, and the lesions commonly had a superficial bulge. Three patients had an initial diagnosis of oxyntic gland adenoma, which was diagnosed as GA-FG after complete resection. These tumors were negative for MUC5AC, but showed diffuse strong positivity for MUC6 and pepsinogen I, and synaptophysin expression. CONCLUSION: GA-FG is a rare gastric tumor with unique morphological features. As it is difficult to diagnose with a biopsy, immunohistochemistry plays an important role in the differential diagnosis. Oxyntic gland adenoma can be regarded as the intramucosal stage of GA-FG. Although all patients were negative for MUC5AC expression, MUC6 and pepsinogen I can help the diagnosis of GA-FG.