Serrated Colon Polyps as Precursors to Colorectal Cancer

Identification of the serrated neoplasia pathway has improved our understanding of the pathogenesis of colorectal cancer (CRC). Insights include an increased recognition of the malignant potential of different types of serrated polyps such as sessile and traditional serrated adenomas. Sessile serrated adenomas share molecular features with colon tumors that have microsatellite instability and a methylator phenotype, indicating that these lesions are precursors that progress via the serrated neoplasia pathway. These data have important implications for clinical practice and CRC prevention, because hyperplastic polyps were previously regarded as having no malignant potential. There is also evidence that the serrated pathway contributes to interval or missed cancers. Endoscopic detection of serrated polyps is a challenge because they are often inconspicuous with indistinct margins and are frequently covered by adherent mucus. It is important for gastroenterologists to recognize the subtle endoscopic features of serrated polyps to facilitate their detection and removal, and thereby ensure a high-quality colonoscopic examination. Recognition of the role of serrated polyps in colon carcinogenesis has led to the inclusion of these lesions in postpolypectomy surveillance guidelines. However, an enhanced effort is needed to identify and completely remove serrated adenomas, with the goal of increasing the effectiveness of colonoscopy to reduce CRC incidence.