Morphological change of foveolar‐type gastric adenocarcinoma after proton pump inhibitor discontinuation in a short time period: A case report

A 37‐year‐old man with systemic lupus erythematosus underwent esophagogastroduodenoscopy as a screening examination for anemia and bloody stool. A semi‐pedunculated edematous lobular polyp of 25 mm in size was detected in the greater curvature of the upper gastric body. At that time, a definitive diagnosis of cancer could not be made based on a biopsy specimen from the lesion. Since the patient was on proton pump inhibitor (PPI) for a long time to prevent peptic ulceration due to prolonged prednisolone administration for systemic lupus erythematosus, we diagnosed the lesion as a PPI‐associated hyperplastic polyp and switched lansoprazole to famotidine. Two months later, esophagogastroduodenoscopy revealed that the polyp had decreased in size to 8 mm, whereas the biopsy specimen led to a histological diagnosis of gastric cancer. The polyp was removed by endoscopic submucosal dissection. Immunohistochemistry revealed that the tumor cells were positive for MUC5AC, but negative for MUC2 and MUC6, leading to a final diagnosis of foveolar‐type gastric adenocarcinoma. In conclusion, we may suggest that PPI induces reversible morphological changes in foveolar‐type gastric adenocarcinoma. Furthermore, short‐term follow‐up of polypoid lesions should be prepared, considering tumor comorbidity with morphological changes during long‐term PPI usage.