We report a case of a hyperplastic polyp that underwent malignant transformation after eradication therapy. The patient was a 76-year-old man who had a 15-mm sized polyp in the fornix of the gastric body. Histologic examination of a biopsy specimen revealed that the lesion was a hyperplastic polyp. Helicobacter pylori infection was confirmed by examining Helicobacter pylori antibodies. After eradication therapy for five months, the polyp decreased to 10 mm in size. After eradication therapy for fourteen months, endoscopy revealed that the polyp had significantly decreased in size, but was accompanied by a localized erosion (IIa+IIc), and biopsy examination showed Group V. Total gastrectomy was performed and the diagnosis of hyperplastic polyp with malignant transformation was confirmed histologically. Our clinical experience and lessons from this case are discussed.
