A Case of a Small Hyperplastic Polyp with Malignant Transformation

Abstract

Small (less than 1 cm) hyperplastic polyps are a common finding on colonoscopy. These polyps are typically removed by gastroenterologists because of an inability to endoscopically distinguish hyperplastic polyps from adenomatous polyps. There is also a controversy whether the presence of hyperplastic polyps pose an increased risk of proximal colonic polyps and risk of future adenomatous polyps and/or carcinoma in the colon. Additionally, virtual colonoscopy (computed tomography colography) has a decreased sensitivity for these small polyps. Arguments for the use of virtual colonoscopy has included that small polyps which may not be detected are typically hyperplastic polyps that do not warrant removal. We report a case of a patient who underwent a colonoscopy and was found to have an infiltrating colon adenocarcinoma arising from a small hyperplastic polyp. A 60 yr old female patient presented with rectal bleeding and subsequently underwent colonoscopy. During colonoscopy a smooth 0.8 cm polyp was identified in the cecum. The polyp was removed by cold snare. Pathology revealed an infiltrating adenocarcinoma arising within the hyperplastic polyp with the margins negative for the tumor. Immunohistochemically, p53 and Ki-67 were positive in the carcinoma portion of the hyperplastic polyp. Although dysplastic (adenomatous) changes in hyperpalstic polyps has been reported, the presence of carcinoma arising in these polyps is rare. This case report suggests that hyperplastic polyps should be removed. Although the risk of carcinoma increases with the size of the polyp and degree of dysplasia, colorectal cancer screening strategies must recognize that all polyps, even small hyperplastic polyps, pose a risk of carcinoma.