Gastric adenocarcinoma of fundic gland type with autoimmune gastritis.

An 87-year-old man with dysphagia presented to our hospital. He was diagnosed with autoimmune gastritis (AIG) with severe atrophy and hypergastrinemia. The patient was positive for parietal cell antibody (PCA) and anti-intrinsic factor antibody (IFA), without evidence of H. pylori infection. A flat elevated tumor was detected in the middle corpus, and therapeutic endoscopic submucosal dissection was performed. Histopathological examination revealed atypical cells mimicking the fundic glands, which were positive for pepsinogen-I and partially positive for MUC6 and H + /K + -ATPase, proliferating to the deep layer. The final diagnosis was gastric adenocarcinoma of the fundic gland type (GAFG). AIG is expected to be difficult to develop GAFG because the basal gastric glands are highly atrophic due to the production of PCA. However, some chief cells may remain and could have the potential to develop into malignancy during AIG progression. Therefore, careful observation is required in patients with AIG when considering the occurrence of GAFG.