Papillary adenocarcinoma occurring in a gastric hyperplastic polyp observed by magnifying endoscopy and treated with endoscopic mucosal resection.

The patient was a 75-year-old man. He had been diagnosed with gastric hyperplastic polyp 4 years previously. The color of the apex of this polyp was whitish. Magnifying endoscopy findings revealed disappearance of the mucosal microstructure with irregular branched capillaries at the top of the polyp. Endoscopic mucosal resection (EMR) was performed. Histological examination revealed that a part of the polyp surface was replaced with papillary adenocarcinoma. Diagnosis of papillary adenocarcinoma in a hyperplastic polyp with mucosal invasion was made. Magnifying endoscopy was useful for the detection of gastric cancer occurring in the hyperplastic polyp in the present case.