A case of fundic gland polyp progressing to carcinoma during six years of follow-up

A 64-year-old woman had received long-term treatment with vonoprazan and prednisolone for eosinophilic granulomatosis with polyangiitis. Annual upper gastrointestinal endoscopy for six years revealed multiple fundic gland polyps (FGPs). A polyp in the gastric fornix increased to 15 mm three years earlier, although biopsy findings at that time were benign. At the most recent examination, repeat biopsy revealed adenocarcinoma, and endoscopic submucosal dissection was performed. Histopathological examination demonstrated parietal cell protrusion (PCP), characteristic of long-term proton pump inhibitor (PPI) therapy, along with surface architectural distortion of the foveolar epithelium and irregular glandular structures consistent with well-differentiated adenocarcinoma. Previous reports have described malignant transformation of FGPs associated with long-term PPI use. When an FGP exceeds 10 mm in diameter and presents with central depression, malignant transformation should be considered.