Although the exact cause of breast cancer is not well understood, several factors related to the development of breast cancer have been identified in domestic and international studies over the years. To summarize, the following risk factors for breast cancer have been identified or are relatively clear: 1. Gender: The risk of breast cancer in women is about 100 times higher than that in men. 2. Age: The risk of breast cancer increases with age. In China, the peak incidence of breast cancer is between 45-55 years old. 3. Menstrual factors: young age of menarche (<12 years old), old age of menopause (>55 years old) and long menstruation time are all risk factors for breast cancer development. 4. Fertility factors: celibacy, older age at menarche (>35 years old) or not having children are risk factors for breast cancer development. 5. Exogenous estrogen: This includes oral contraceptives containing estrogen and the application of estrogen replacement therapy in postmenopausal women. Body mass: Weight gain after menopause is also a risk factor for breast cancer development. Some studies suggest that a tall body is also a risk factor for breast cancer. Dietary factors: Alcohol consumption and high fat diet can increase the risk of breast cancer. Geographical, racial, economic and cultural factors: Globally speaking, the incidence of breast cancer is highest in North America and Northern Europe. The incidence of breast cancer is higher in women of high economic and cultural levels than in rural women. 9. History of breast diseases: Those who have had benign breast diseases and pathologically confirmed atypical hyperplasia, those who have a history of in situ breast cancer, and those who have had breast cancer on one side will have higher risk of breast cancer. 10. Family history of breast cancer: Breast cancer has a certain tendency of family clustering. 11. Ionizing radiation: exposure to moderate to high doses of ionizing radiation in the chest can increase the risk of breast cancer. 12. Embryonic gene mutation: such as BRCA1, BRCA2 gene mutation, P53 gene mutation, etc. Factors that have been proven to have protective effects on breast cancer include breastfeeding, regular physical activity, multiple births, and being overweight at a young age.