1. Marriage and childbirth. Epidemiological studies show that women who are married but do not have children or whose first child is born after 30 years old are also unfavorable factors, but the risk of breast cancer in unmarried people is twice as high as that in married people. Experts believe that childbirth has a protective effect on the breast, but only for those who had a full-term birth before the age of 30. Some studies have shown that women whose first pregnancy is older than 30 years old have a slightly higher risk of breast cancer than women who have never given birth, and it is believed that breastfeeding has a protective effect on the occurrence of breast cancer, mainly in premenopausal women. 2.Ionizing radiation. The breast is a tissue that is more sensitive to the carcinogenic activity of ionizing radiation. When young, the mammary gland is the most sensitive to the carcinogenic effect of ionizing radiation during the mitotic activity stage, and the effect of ionizing radiation is cumulative, with the same risk level of multiple small dose exposures and one large dose exposure, with a dose-effect relationship. 3. Patients who have previously suffered from breast cancer or have a history of benign breast tumors, suffer from certain chronic breast diseases (such as ductal epithelial atypical hyperplasia, papillomatosis, etc.), have an increased risk of breast cancer. 4. Hormones. Breast cancer is related to the imbalance of human endocrine balance. Among various endocrine factors, the most important ones are estrogen and progesterone. Research results show that estrogen stimulates excessive proliferation of epithelial cells in breast glands, which is an important cause of breast cancer. Women who apply estrogen to control menopausal symptoms have a moderate increase in the risk of breast cancer after many years. Taken together, these eight factors basically constitute the general framework of the incidence pattern of breast diseases in China.