Hyperplastic Polyps May Increase the Risk for Colorectal Cancer: 2011 ACG Presidential Poster

Abstract

Purpose: Hyperplastic (HP) polyps are found in up to 30% of asymptomatic adults over the age of 50. Patients with these polyps are currently not considered at any increased risk for developing colorectal cancer. According to current guidelines, the presence of HP polyps found during a flexible sigmoidoscopy, is not an indication for colonoscopy. In addition, when identified during a colonoscopy, the recommended follow up surveillance is every ten years. DNA instability has been identified in right colonic HP polyps and multiple HP polyp syndrome. In this study, HP polyps were evaluated for active cell growth and the presence of p53 genetic mutation. Methods: Twenty patients with HP polyps were randomly selected and ten control patients (5 sessile serrated adenoma biopsies and 5 normal colonic mucosa biopsies) were selected. The colonoscopies were previously performed at Space Coast Endoscopy Center, within the past three years. The tissues were evaluated using immunohistochemistry stains. A Ki-67 stain was used to determine proliferative activity by positive nuclear staining of epithelial cells in the non-G0 portion of the growth cycle. The immunohistochemical stain for p53 was employed to detect over expression of the p53 nuclear protein resulting from mutation or functional inactivation of the p53 gene. A One Proportion Confidence Test was used to show the statistical significance of the results. Results: HP polyps were positive for the p53 mutation in 40% of the polyps. None of the HP polyps stained positive for Ki-67. In the control group, 40% of the sessile serrated adenomas stained positive for the p53 mutation and 60% stained positive for Ki-67. None of the normal mucosa stained positive for Ki-67 or the p53 mutation. Based on the experimental data, statistics show with 95% confidence that the percent of all HP polyps that will test positive for the p53 mutation is within 18% and 61%. Conclusion: Hyperplastic polyps may contain genetic mutations that seem to increase their risk of developing into colorectal cancer. It is possible that other mutations may also exist. It is therefore, not known if HP polyps may progress to serrated adenomas and then to cancer, or if they progress directly to colorectal cancer independently. More studies are needed utilizing immunohistochemistry staining. It appears that patients with HP polyps would benefit from more frequent colonoscopy surveillance than is currently recommended.