Endoscopic and clinicopathological features of gastric adenocarcinoma of fundic gland mucosa type: a case report and literature review

Background: Gastric adenocarcinoma of fundic gland mucosa type (GA-FGM) is a low-grade atypia and well-differentiated adenocarcinoma. Thus far, ten cases of GA-FGM have been reported in the literature. We report a case and discuss the clinicopathological features of GA-FGM to improve the understanding and diagnosis of GA-FGM. Methods: We retrospectively reviewed the clinical, endoscopic, histological, and immunophenotypic features and treatment of 1 case of GA-FGM, and combined this with literature discussion. Results: This is a 52-year-old male patient who underwent upper gastrointestinal endoscopy and was found to have a type IIc lesion on the upper part of the stomach. Most of the surface of the cancer tissue was covered with normal epithelium as observed under low magnification. The surface of the focal mucosa was covered with tumorous gastric pit epithelial cells. Deep tumors are mainly composed of a large number of eosinophils and a small number of gastric pit cells, which are mottled. Tumor cell nucleus showed mildly atypical characteristics with loss of nuclear polarity and visible nuclear fission. The glandular structure had significant atypia. Tumor invaded the submucosa. Immunohistochemistry showed that MUC5AC was positive on the surface and deep pit-epithelial-like tumor cells. The deep cancer tissues were widely positive for pepsinogen I (pepsin A) and H+/K+-ATPase, and some cancer cells expressed MUC6. The Ki-67 proliferation index was approximately 3%. Conclusions: GA-FGM is a rare new histological type of gastric cancer. The possibility of GA-FGM should be considered when the gastric intrinsic mucosal epithelial cells are mildly atypical and the fundic gland structure is markedly atypical and the distribution pattern of the relative normal mucosal immune phenotype was observed, especially in biopsy specimens.