1, genetic factors, part of breast cancer is hereditary, mainly carrying mutations of oncogenes BRCA1 and BRCA2. Women who carry these two mutations have a 50-80% chance of developing breast cancer in their lifetime. Currently, there is no laboratory testing for these two genes in China. Hereditary breast cancer accounts for 5-10% of all breast cancers. In addition to BRCA1 and BRC2, there are several other genes related to hereditary breast cancer such as TP53, PTEN and ATM, all of which are autosomal dominant. Breast cancer, like other cancers, has family aggregation. A woman with breast cancer is 2-3 times more likely to have a first-degree relative (mother, daughter, or sister) with breast cancer than the general population. Other blood relatives have a slightly higher incidence rate. The incidence of breast cancer in women varies significantly among different countries, with the highest incidence in the United States and Northern Europe, the middle incidence in Southern Europe and Africa, and the lowest incidence in Asia. The incidence rate is highest among Caucasians, followed by Blacks and lowest among Yellows. The incidence rate of female breast cancer is closely related to age. 5.Reproductive factors, young age of menarche (less than 12 years old), late menopause (more than 55 years old), old age of first full-term birth, few births, and not breastfeeding are risk factors for breast cancer. 6. Endogenous hormone factors, excessive estrogen, progesterone and lactogen in women are risk factors for breast cancer. 7. Exogenous hormone factors, exogenous estrogen supplementation after menopause is a risk factor for breast cancer. 8. Alcohol intake is a risk factor for breast cancer. 9. Excessive ionizing radiation to the breast is a risk factor for breast cancer. 10. Physical activity is a protective factor for breast cancer. 11. There is no definite basis for the relationship between smoking, high fat and high calorie diet and breast cancer. 12. The relationship between environmental pollution and breast cancer has no definite basis. 13. There is no clear basis for the relationship between mental status and breast cancer. 14. There is no definite relationship between breast silicone implants and breast cancer incidence. 15. There is no definite relationship between oral contraceptives and the incidence of breast cancer. 16. The relationship between phytoestrogens, (mainly contained in soy products) and breast cancer incidence is not clear. The factors closely related to the occurrence of breast cancer are listed here, but I would like to make a special note: the occurrence and development of breast cancer is a multifactorial interaction and a very complex process. For example, many women carry a heavy burden because their mothers, sisters or other blood relatives have breast cancer, some women worry because they have not given birth and are not breastfeeding, some women worry because they have silicone implants, etc. It is not advisable. In addition, although there is no clear relationship between some factors and the occurrence of breast cancer, such as mental state, if a person is always in a depressed, depressing, stressful and anxious inner world, she will have a higher chance of developing various diseases, and breast cancer is no exception.