Women who menstruate early (earlier age of first menstruation) may have an increased chance of developing breast cancer, but there is not necessarily a definite relationship. Breast cancer is the most common malignant tumor in women. The main clinical manifestations are breast lumps, nipple discharge, and enlarged axillary lymph nodes. Surgical resection is the main treatment method, and radiotherapy, chemotherapy, targeted therapy and endocrine therapy can be given after surgery. Since the mammary gland is the organ of action of many endocrine hormones, estrogen level is directly related to the development of breast cancer. Risk factors also include early age of menarche, late age of menopause, infertility, late age of the first childbirth, family history of breast cancer, history of benign breast diseases, and estrogen replacement therapy after menopause, etc. Other factors include marriage, breastfeeding, and the risk of breast cancer. Other factors include marriage, breastfeeding, lifestyle habits, mental factors, and obesity. Although breast cancer is the result of a combination of multiple disease-causing factors inside and outside the body under certain conditions, the presence of high-risk factors increases the risk of developing the disease.