When colonoscopy reveals colon polyps, I believe all patients will ask the same question: Will my polyps become cancerous? And they are more or less anxious about it. In fact, 95% of colorectal cancers evolve from polyps, but less than 10% of adenomatous polyps become cancerous, some polyps are prone to cancer and some are not. Depending on the nature of the polyps, colorectal polyps are classified as inflammatory polyps, hyperplastic polyps, and adenomatous polyps. Inflammatory and hyperplastic polyps are generally not cancerous, while adenomatous polyps may become cancerous. Recent studies have also shown that some polyps that have long been considered benign may also develop cancer. For this reason, doctors usually remove all polyps found during a colonoscopy.
The next question would be which polyps are prone to cancer?
Adenomatous polyps can be divided into tubular adenomas, villous adenomas, and villous tubular adenomas (mixed type) depending on their general shape. Tubular adenomas have the lowest cancer rate, while villous adenomas have the highest cancer rate. Depending on the heterotype, adenomatous polyps can be subdivided into low-grade intraepithelial neoplasia and high-grade intraepithelial neoplasia, with the latter having a higher risk of cancer. In addition, the malignancy rate is also related to the size of polyps, with the rates of malignancy for polyps less than 1 cm, 1-2 cm, and greater than 2 cm being 1%, 10%, and 35%, respectively. The malignancy rate is 10% for choriocapillaris less than 2 cm in diameter and up to 53% for those larger than 2 cm. Recent findings suggest that serrated adenomas are also highly susceptible to cancer and should be taken seriously.
How do colorectal polyps develop into colorectal cancer?
Under the action of various carcinogenic factors, the colonic mucosa becomes overgrown; the overgrown mucosa slowly forms small adenomatous polyps; the polyps gradually grow up to form large adenomatous polyps; then heterogeneous hyperplasia occurs; when the heterogeneous hyperplastic tumor cells invade the submucosa, it becomes early colorectal cancer; the tumor cells continue to grow inside the intestinal wall from inside to outside, then invade the tissues outside the intestinal wall, and The tumor cells continue to grow inside the intestinal wall from inside to outside, and then invade the tissues outside the intestinal wall, and also metastasize to distant places along the lymphatic vessels and blood vessels, which forms middle and late stage colon cancer. Scientists at Johns Hopkins Hospital have also described the genes involved in the cancerous process of colorectal polyps. They concluded that the development of colorectal polyps and colorectal cancer is the result of gene mutations or other chemical modifications. Genes such as APC, K-ras, Bat-26 and P53 are involved in the carcinogenesis of colorectal polyps. The development of early adenomatous polyps into advanced adenomatous polyps is expected to take about 2-5 years. Similarly, advanced adenomas are estimated to take about 2-5 years to develop into early colorectal cancer.