Large duodenal pyloric gland adenoma successfully resected by endoscopic submucosal dissection

A 71-year-old woman was given a barium meal examination as part of a workup for recurring melena and iron deficiency anemia (IDA), and it revealed a large duodenal polyp measuring 60 mm in diameter. Subsequent upper gastrointestinal endoscopy showed a large pedunculated polyp in the duodenal bulb. Magnifying endoscopy with narrow-band imaging (NBI) showed that the lesion consisted of a regular enlarged intervening part between crypts of the epithelium that resembled gastric mucosa. Although the lesion was suspected of being benign, it was resected by endoscopic submucosal dissection (ESD) to prevent the progression of the IDA. The pathology examination revealed the proliferation of mildly irregular-shaped or dilated glands lined by cuboidal cells and low columnar cells in the submucosa. The gastric glands were immunohistochemically positive for MUC6, suggesting pyloric gland differentiation. The lesion was covered by a foveolar-type epithelium, and we made a diagnosis of pyloric gland adenoma (PGA). PGAs are most common in the stomach, and they are rare in the duodenum, where endoscopic treatment is technically challenging. Here we report a case of large duodenal PGA successfully resected by ESD. Since part of PGAs has been reported to be associated with adenocarcinoma, minimally invasive treatment strategies are desirable to reduce the risk of progression to carcinoma.