Can rectal polyps become cancerous? This is a question that many patients are concerned about. Generally speaking, rectal polyps in childhood are less likely to become malignant. In adults, as the size of polyps grows, the cancer rate increases. The total cancer rate is about 10%-20%. There are two theories for the carcinogenesis of polyps, namely, that various carcinogenic factors firstly form adenomatous polyps in the intestine, and then carcinogenesis on this basis, so it is recognized that polyps are precancerous lesions, especially adenomas, villous adenomas, or papillary adenomas, which have the tendency to become malignant; the second is the theory of neoplastic carcinoma, that is, without going through the process of adenoma, but under the action of carcinogenic factors, from normal mucosa directly to cancer. It is generally believed that the cancer rate of polyps increases with the growth of their volume. The majority of polyps less than 0.5cm are benign, and the cancer rate is only 0.6%; below 1.0cm, it is about 6%; above 2.0cm, the chance of cancer increases up to 20%; above 4cm, it is mostly malignant. From pathological histological analysis, the cancer rate of tubular adenoma is about 5%, that of mixed adenoma is 20%, and that of villous adenoma is more than 50%. Polyps with irregular morphology, rapid growth and faster enlargement are more likely to become cancerous, and broad-based polyps are more likely to become cancerous than polyps with tissues. According to statistics, the cancer rate of tubular adenomas in the rectum is 7.3% and in the sigmoid colon is 24.8%.