Cancer cells and normal cells evolve slowly in the process of growth and differentiation, and the differences become more and more obvious. Precancerous lesions have a process where cancer cells, i.e. cells, have some mutations that cause some biological behavior to change. The disease also has a slow development process in tissues and organs, such as some changes in cell morphology and tissue structure, which is the process of slowly evolving into malignant tumors. For example, in the process of intestinal cancer, we can see a series of evolutionary processes, some polyps slowly turn into intestinal cancer; in the process of stomach cancer and breast cancer development, we can also find precancerous lesions exist, like stomach cancer, some chronic atrophic gastritis slowly evolves into stomach cancer, and breast cancer slowly evolves into breast cancer in benign breast tumor. Therefore, many tumors have precancerous stages in the process of development, which are valuable for tumor prevention and treatment. Early detection of these precancerous lesions, early diagnosis and treatment can reduce the chance of precancerous lesions developing into cancer and get a good treatment effect, so it also increases the effectiveness of cancer prevention and treatment.