The exact cause of the development of breast cancer is still unclear and cannot be explained by a single factor. It is generally believed that the occurrence of breast cancer is related to the following factors 1. Early menarche and late menopause. The relative risk of breast cancer increases 2.2 times when the age of menarche is less than 12 years old compared to more than 17 years old. The age of menopause is greater than 55 years old and the risk of breast cancer is 1 times higher than that of those younger than 45 years old. Early menarche and late menopause are the two main risk factors for breast cancer. 2. Genetic factors. It has been found that women whose mothers had bilateral breast cancer before menopause have 9 times higher risk of breast cancer than the average woman, and the average age of breast cancer in the second generation of breast cancer patients is about 10 years earlier than the average person. The average age of the second generation of breast cancer patients is about 10 years earlier than that of the general population. Women who have sisters with breast cancer have three times the risk of the general population. It is important to emphasize that breast cancer is not directly inherited, but is a kind of “cancer quality” inheritance, and the relatives of breast cancer patients do not necessarily have breast cancer, but are more likely to have breast cancer than the general population. 3. Marriage and childbirth. Epidemiological studies show that women who are married but do not have children or have their first child after the age of 30 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. Recent studies have concluded that breastfeeding has a protective effect on the occurrence of breast cancer, mainly in premenopausal women. 4.Ionizing radiation. The breast is the tissue that is more sensitive to the carcinogenic activity of ionizing radiation. When young, the mammary gland mitotic activity stage is the most sensitive to the carcinogenic effect of ionizing radiation, and the effect of ionizing radiation has a cumulative nature, multiple small dose exposure and a large dose exposure to the same degree of risk, with dose-effect relationship. Among the survivors of the atomic bombing in Nagasaki, Japan, the proportion of breast cancer has increased significantly, and those who received chest radiotherapy during childhood and adolescence have an increased chance of breast cancer when they grow up. 5. Unhealthy eating habits. There is a strong correlation between the incidence and mortality of breast cancer and the amount of fat digested per capita. The high income of some company employees leads to a high standard of living, resulting in an unscientific and unhealthy “high-calorie, high-fat” diet, which leads to a much higher incidence of breast cancer. 6. Unhealthy lifestyle. Some female white-collar workers who are engaged in office work for a long time sit more and move less, lack of exercise and less exposure to sunlight. Most professional women, due to their work, spend a lot of time with their bras tightly closed, rarely giving their breast glands a “break”; some professional women are forced by the pressure of work or the pursuit of career success to live a single noble or dinky life, without a family, without children. These factors are related to mastopathy. 7, mental depression and excessive tension. According to the survey, introversion, long-term mental depression and unhappy early life are important factors leading to cancer. Young urban women face fierce competitive pressure and their spirits are in a state of stress and tension for a long time, leading to emotional instability and unrest. These mental factors and bad life and work style together cause further damage to breasts. 8.Hormones. Breast cancer is related to the imbalance of human endocrine balance. Among the various endocrine factors, the most important ones are estrogen and progesterone. Research results show that estrogen stimulates excessive proliferation of breast glandular epithelial cells, which is an important cause of breast cancer. The frequent use of hormone supplies and hormone replacement therapy for women during menopause can increase the risk of breast cancer. 9.Drugs. Some drugs, such as blood pressure drugs like reserpine and phenothiazole, and steroids have the effect of increasing the prevalence of breast cancer. Some health products, skin care products and cosmetics contain cancer-causing ingredients and should be used with special caution. In addition, harmful ingredients in the air and pesticide residues on vegetables and fruits have different degrees of carcinogenic ingredients.