A good friend of mine had a colonoscopy this year due to abdominal discomfort and occasional blood in the stool, and found a 1.5cm polyp in his large intestine, which he was afraid would turn into colorectal cancer, so he consulted me about it. I told him that the polyp was benign and there was no need to worry too much, but it had to be removed, and after removal, the test was a benign adenoma. It takes at least 10 years to develop from normal colon to colorectal cancer, which usually evolves gradually from normal colon → colorectal adenoma → colorectal cancer. Colorectal adenoma is the precancerous lesion in the process of colorectal cancer development. As long as we find and remove colorectal adenoma in time, we can ensure that no cancer will occur if colorectal cancer is strangled at the precancerous lesion stage. Scientific understanding of precancerous lesions Precancerous lesions refer to benign lesions that appear before malignant tumors and have a certain degree of heterogeneous proliferation in cell morphology and have the potential of cancerous changes. Precancerous lesions are usually the prelude to the development of cancer and are often divided into three periods: mild, moderate and severe. For example, the development process of gastric cancer often goes through normal gastric mucosa → superficial gastritis → atrophic gastritis → mild to moderate heterogeneous hyperplasia → severe heterogeneous hyperplasia/carcinoma in situ → early gastric cancer → advanced gastric cancer, and the appearance of mild to moderate heterogeneous hyperplasia in gastric mucosa cells is often a reversible process, which can be transformed to normal gastric mucosa if treated in time. If it develops into severe heterogeneous hyperplasia, it is very dangerous and may develop into gastric cancer if not treated in time. Do not take general “hyperplasia” as precancerous lesions in life, only when the cell shape appears “heterogeneous or atypical hyperplasia” is a real precancerous lesion. Pre-cancerous lesions do not have to be feared because they do not have malignant characteristic changes and are essentially different from cancer, and most of them do not turn into cancer, and only a few of them develop into cancer. How to detect precancerous lesions Common precancerous lesions include: (1) Respiratory system: papilloma of nasal cavity and larynx, white spots of vocal cords, atypical hyperplasia of bronchial mucosa epithelium. (2) Digestive system: esophageal squamous epithelial atypia or Barrett’s esophagus, atrophic gastritis and gastric ulcer, chronic ulcerative colitis, colorectal adenoma. (3), genitourinary system: inversion papilloma of the bladder, cystic hyperplasia of the breast, fibroadenoma of the breast, cervical erosion with atypical hyperplasia. (4), skin and mucous membrane: persistent skin ulcers, mucosal leukoplakia, proliferative scars. Most patients with precancerous lesions do not have obvious clinical symptoms, so it is difficult to detect precancerous lesions. Clinically, it is found that people with some bad habits often have precancerous lesions, such as papilloma of the larynx, white spots on the mucous membrane of vocal cords and atypical hyperplasia of esophageal squamous epithelium in people who smoke and drink a lot of alcohol for a long time; atrophic gastritis and gastric ulcer in people with high work pressure and irregular diet; colorectal polyps in people with high fat diet and too little exercise, therefore, for people with bad habits Regular physical examination is the most effective means to detect precancerous lesions. Pre-cancerous lesions of the digestive system can be detected by endoscopic examination, such as esophageal cancer, which can be clearly detected by endoscopic iodine staining. Gynecological precancerous lesions can be detected by cervical cytology and colposcopy. For breast precancerous lesions, ultrasound, X-ray and palpation can be chosen. How to treat precancerous lesions Sun Yan, academician of Cancer Hospital of Chinese Academy of Medical Sciences, pointed out that “intervention of precancerous lesions is the key to prevent cancer”, so precancerous lesions found should be treated actively. For mild and moderate precancerous lesions, observation and close follow-up can be carried out by changing poor lifestyle and habits, while for severe precancerous lesions, minimally invasive treatment can be chosen, which basically has no impact on the quality of life after treatment. For precancerous lesions in the gastrointestinal tract (esophagus, stomach, colon) and respiratory tract (larynx, bronchus), mucosal resection or polyp removal can be performed by endoscopic means. Precancerous lesions in gynecology can be treated by physical therapy such as laser, freezing, electrocoagulation and simple surgery. IV. Conclusion Malignant tumor is one of the major diseases that seriously endanger human health. With the deepening of people’s understanding of cancer, prevention is found to be the most effective weapon to fight against cancer. Academician Cheng Shujun from Cancer Hospital of Chinese Academy of Medical Sciences pointed out that the key to human being’s ultimate control of tumor should not be in the middle and late stage, but should advance from middle and late stage tumor to early stage, precancerous lesion or even susceptible stage. The best way to keep away from cancer is to shift the front of fighting against tumor and prevent the disease before it happens.