Large Fundic Gland Polyp Associated with Long-Term Proton Pump Inhibitor Administration Mimicking Gastric-Type Neoplasm

A 57-year-old man with a 10-year history of proton pump inhibitor (PPI) use presented with multiple fundic gland polyps (FGPs) including one >20 mm, whitish, semi-pedunculated polyp. Black spots and cobblestone-like mucosa were also observed in the stomach upon endoscopy; therefore, the lesion was considered to result from long-term PPI administration. Endoscopically, we diagnosed this polyp as a neoplastic lesion with gastric phenotype rather than a non-neoplastic lesion. Biopsy revealed an atypical glandular lesion that was indeterminate for neoplasia; therefore, we performed en bloc resection via endoscopic submucosal dissection (ESD) of the 22 × 22 × 10 mm-sized polyp. Histologically, the polyp was composed of hyperplastic foveolar epithelia in the upper half of the mucosa and hyperplastic fundic glands in the lower half of the mucosa, with luminal dilatation and parietal cell protrusion. The pathological diagnosis for this ESD specimen was FGP associated with PPI administration. We herein describe this rare case of a large FGP in Helicobacter pylori-uninfected gastric mucosa associated with long-term PPI administration, which was mimicking gastric-type neoplasm and resected by endoscopy.