A case of malignant transformation of a hyperplastic prepyloric polyp changing from a semipedunculated polyp to a superficial depressed lesion after eradication of Helicobacter Pylori

This is a 60-year-old woman diagnosed with malignant transformation of a hyperplastic polyp changing the appearance from a semipedunculated polyp to a depressed lesion after eradication of Helicobacter pylori (H. pylori). The patient underwent upper gastrointestinal endoscopy, which revealed a large (20 mm) gastric hyperplastic polyp of the prepyloric anterior wall. In the course of observation at 8 months after eradication of H. pylori, the polyp has decreased in size and has changed, with appearance of erosions. After 14 months, the polyp has become a 5 mm-sized depressed lesion. The biopsy specimen revealed a well to moderately differentiated adenocarcinoma, and the lesion was resected by endoscopic submucosal dissection. The possibility of the presence of a hyperplastic polyp from the beginning that underwent malignant transformation was considered. Thus, a hyperplastic polyp requires detailed observation before and after eradication of H. pylori.