Breast cancer is the most common malignant tumor in women and poses a serious health risk to women. About 1.2 million women worldwide suffer from breast cancer every year, and about 500,000 women die from breast cancer. The incidence rate of breast cancer in China is lower than that in Europe and the United States, but it is increasing at a rate of 2%-3% every year, and the peak age of incidence is 40-55 years old, about 10 years earlier than that in Europe and the United States. In Shanghai, Beijing and some coastal cities, the incidence rate of breast cancer reaches 40-50/100,000, and the incidence rate of breast cancer has surpassed cervical cancer to become the No. 1 malignant tumor among women. Research shows that the occurrence of breast cancer is related to the following risk factors: 1. Hormone secretion disorder Breast cancer is a hormone-dependent tumor, and the increase of estrogen level in the body is an important cause of breast cancer, including endogenous estrogen and exogenous estrogen. The increased secretion of estrogen in the body can make the ductal epithelial cells of the breast overproliferate and become cancerous. In addition, early age of menarche (less than 12 years old), late menopause (later than 55 years old), physical obesity, high-fat and high-calorie diet can enhance or prolong the stimulation of estrogen on breast epithelial cells, and increase the probability of breast cancer development. Long-term use of estrogen (such as birth control pills, hormone replacement therapy) or estrogen-containing supplements can also trigger breast tumors. 2. Fertility Factors Later age of first pregnancy, infertility, and lower number of births in menstruating mothers are also identified as risk factors. The risk of developing breast tumor increases by 5% for each year the age of first birth exceeds 35 years, and decreases by 7% for each additional birth after that. Several studies have shown that shorter intervals between births are associated with a lower lifetime incidence of breast cancer. 3. Breastfeeding factor The total duration of breastfeeding is negatively correlated with the risk of breast cancer. According to a survey, the risk of breast cancer is 2 to 3 times smaller for breastfeeding mothers than for non-breastfeeding mothers, and the longer the breastfeeding time, the less chance of breast cancer. 4. Chronic breast diseases and benign tumors Cystic hyperplasia of breast with atypical hyperplasia is a kind of pre-cancerous lesion, which can easily turn into breast cancer. Some benign tumors also have the possibility of malignant transformation. 5. Genetic factors Breast cancer has an obvious tendency to run in families. Epidemiological survey found that 5%-10% of breast cancers are familial. If one first-degree relative has breast cancer, the risk of the disease increases 1.5-3 times, and if two first-degree relatives have breast cancer, the risk of the disease will increase 7 times. The younger the age of first-degree relatives, the greater the risk of breast cancer among relatives. 6. Bad mood and mental stress Long-term depression or depression and excessive mental stress are the main risk factors for breast cancer. In clinical work, we have come into contact with a large number of breast cancer patients. Most of them have some commonalities in their personalities, such as impatience, often uncovering or depression due to trivial things in life, and excessive mental stress caused by life and social factors, etc. Studies have confirmed that the relative risk of breast cancer for women who have experienced serious adverse life events can be increased by 2 to 3 times. 7. Bad lifestyle Staying up late, long-term smoking, alcoholism, lack of exercise, unscientific bra wearing, unhealthy diet such as heavy oil, deep-fried, smoked and pickled food, habit of drinking coffee and eating chocolate are also risk factors for breast cancer. 8. Certain occupational and environmental factors Exposure of human body to radiation, especially in childhood, can increase the probability of breast cancer in adulthood. In particular, girls who receive breast irradiation because of early cancer have a higher risk of developing breast cancer. Environmental pollution and various types of radiation exposure may also be associated with breast cancer. The fact that the incidence of breast cancer in developed areas is higher than that in non-developed areas indicates that there is a relationship between living environment and the development of breast cancer. In conclusion, women with the above risk factors do not necessarily have breast cancer, but have a higher risk of developing breast cancer than normal people. Breast cancer is a chronic disease with multiple causes, multiple stages and multiple genetic mutations. It is not only caused by a single intrinsic factor (e.g. genetic defects) or a single extrinsic factor (e.g. carcinogenic factors) alone, but is the result of the alternating and interactive effects of multiple factors. By understanding the risk factors of breast cancer, we should try our best to reduce the incidence of breast cancer by avoiding them if they are present and preventing them if they are not. Early detection, early diagnosis and early treatment can better improve the cure rate of breast cancer!