Precancerous lesions are benign lesions with cancer potential. Precancerous lesions of breast cancer mainly include ductal epithelial atypical hyperplasia, flat epithelial atypical hyperplasia, lobular atypical hyperplasia, papilloma with ductal epithelial atypical hyperplasia and abnormal hyperplasia, radioactive scar, ductal carcinoma in situ, lobular carcinoma in situ, etc. Precancerous lesions do not necessarily develop into cancer, nor do all cancers come from precancerous lesions, but some benign lesions with cancerous potential may be transformed into cancer if they are not treated in time. Therefore, it is important to prevent precancerous lesions from occurring, and patients should have regular self-breast examinations and ultrasound mammograms. In case of suspected lesions, hollow needle aspiration biopsy histological examination should be performed to clarify the nature of lesions and to achieve early detection and treatment.