When it comes to breast cancer, many women are doubly concerned about it. However, it is important to know that it is a long process to develop from precancerous lesions to breast cancer. If precancerous lesions of breast cancer can be detected in advance and treated in time, it is an important means to stop the process of breast cancer. 1.What are precancerous lesions of breast in 2012, the World Health Organization’s histological classification of breast tumors, the histological classification of precancerous lesions of breast include: (1) ductal carcinoma in situ; (2) lobular tumors: lobular carcinoma in situ and lobular atypical hyperplasia; (3) atypical ductal hyperplasia. There are also internationally recognized precancerous lesions of the breast: (1) ductal and lobular atypical hyperplasia; (2) columnar epithelial atypical hyperplasia; (3) lobular carcinoma in situ; (4) papillary lesions; (5) proliferative radiological scarring. In summary, most physicians’ opinions, consider atypical ductal epithelial hyperplasia, atypical lobular hyperplasia and papillary neoplasia as the most dangerous precancerous breast cancer lesions. These pre-cancerous breast lesions can be detected in the hospital. 2. Who are prone to precancerous breast lesions (1) Older women who have given birth at full term. (2) Older women who have never given birth. (3) Family history of breast cancer. (4) Those with high social or economic status. (5) Early menarche. (6) Those who have benign breast diseases. 3.How to detect breast cancer precancerous lesions in the early stage. Previous history of breast enlargement, recent change in the nature of breast pain, thickening of breast gland outside the area of breast enlargement. Self-examination of breast lumps, yellowish, colorless or red nipple overflow, change in color of nipple and areola area, darkening of color and lack of luster. Breast ultrasound reveals abnormal solid hypoechoic nodules with irregular morphology and poorly defined borders, with punctate calcifications or abnormally increased blood supply found within or around them. Mammogram found tiny calcified foci or nodular shadow. 4.How to treat breast cancer precancerous lesions Currently, physical and chemical interventions are mainly adopted for breast cancer precancerous lesions. In addition, biological and social interventions should not be neglected. The so-called biological intervention is to regularly follow up those with genetic family history and positive gene mutation test and take corresponding intervention measures. The so-called social intervention is mainly to change the bad habits and pay attention to diet and exercise.