The so-called precancerous lesions are benign diseases that may be transformed into cancer in the future, but not necessarily into cancer. Clinically, common precancerous lesions include familial colonic polyposis, colonic villous adenoma, colonic tubular adenoma, leukoplakia, staining dry skin disease, giant chronic gastric ulcer, gastric polyp, chronic atrophic gastritis with intestinal epithelial hyperplasia, chronic skin ulcer, etc. In addition, epithelial atypical hyperplasia of organs is also treated as precancerous lesions, such as severe atypical hyperplasia of cervicitis, endometrium with severe atypical hyperplasia, and severe atypical hyperplasia of ductal epithelium of breast. At present, no treatment is needed for precancerous lesions, but they should be closely followed up and monitored for changes, and prompt treatment should be given as soon as changes occur.