Understanding colorectal polyps to prevent colorectal cancer

Abstract

Background: Colorectal cancer (CRC) is one of the leading causes of cancer-related mortality worldwide. Most CRCs arise through carcinogenesis pathways from precancerous lesions, such as adenoma and sessile serrated lesions (SSLs). Understanding the characteristics of such precancerous colorectal polyps and the carcinogenesis pathways helps to develop CRC preventive strategies via screening, colonoscopic polypectomy, and surveillance.Current Concepts: Benign colorectal tumors can be classified as conventional adenomatous and serrated polyps. Conventional adenoma is one of the most prevalent precancerous polyps detected on screening colonoscopy, but most are small. Small colorectal adenomas are less likely to contain advanced histology, such as villous features, high-grade dysplasia, or invasive cancer. A small adenoma may progress slowly over 10 years to become an invasive cancer via the chromosomal instability pathway. SSL is a recently established precancerous lesion and is estimated to account for approximately 15% of sporadic CRC. Most SSLs are not dysplastic and progress very slowly through the serrated carcinogenesis pathway. Conversely, SSL with dysplasia (SSLD) may progress more rapidly, as a mismatch repair gene product is defective. According to colonoscopy studies, SSLD comprises only 4% to 8% of SSLs, with a prevalence of 0.1% to 0.9%. Most precancerous lesions detected on colonoscopy progress slowly to CRC and are appropriate targets for colonoscopic polypectomy for the prevention of CRC.Discussion and Conclusion: Colorectal adenoma and SSL are representative precancerous lesions of CRC and most are slow progressing enough to be detected and removed via colonoscopy before CRC development.