There are many risk factors for developing breast cancer. In addition to the genetic, endocrine, and viral factors highlighted earlier, there are a number of other important risk factors that occur frequently or are often present in breast cancer patients. The presence of one or several risk factors does not mean that the patient will or is susceptible to breast cancer, but simply that the patient is statistically more at risk than the general population, but the patient’s risk of getting breast cancer may still be quite small. The author raises this issue with the main purpose of popularizing and improving knowledge about cancer prevention. The important risk factors are: 1. Gender: More than 99% of breast cancers occur in women, which is the “most vulnerable women”. 2. Age: Breast cancer is mainly a disease of middle-aged and elderly people in China. 3. History of pre-cancerous breast lesions: Those who have lobular carcinoma in situ or non-invasive ductal carcinoma have a significantly higher chance of developing wet breast cancer. Clinical and statistical data indicate that cystic breast disease may be a carcinogenic factor and is confirmed by external harvest or biopsy. In women with cystic breast disease, the chance of developing breast cancer is 2.5 to 4 times greater than that of the average woman. If cystic hyperplasia is also associated with active epithelial cell proliferation, the incidence of breast cancer is 4 to 7 times greater than normal. Intraductal papillomas have the potential to become cancerous. Rarely, papillomatosis is also a precancerous lesion. 4. Personal history of breast cancer: After treatment of breast cancer on one side, the chance of breast field change on the opposite side is 5 times greater than the chance of first breast cancer in general women. It is believed that if one side of breast cancer occurs in women with a family history of breast cancer, their family history has 3 possibilities: ① their relatives’ breast cancer often occurs before menopause and invades both breasts. (ii) Breast cancer in their relatives is most often of central type. (3) Their relative’s contralateral breast has precancerous lesions. And the chance of cancer in their contralateral breast is especially high. Dietary habits: The high incidence of breast cancer in women with high-fat diet has attracted the attention of clinicians and scientists. 6. Menstrual status: The earlier the menarche, the higher the chance of breast cancer in the future. According to some statistics, the chance of breast cancer is 20% less for those who are above 14 years old than those who are below 12 years old. The later the menopause, the greater the chance of developing breast cancer. According to some statistics, those who have menopause at the age of 55 or above have one time more chance of getting breast cancer than those who have menopause at the age of 50 or below. Breast cancer that occurs after menopause is mostly seen in obese women, while breast cancer that occurs before menopause is mostly seen in thinner women. The risk of breast cancer is 4 times less for those who give birth for the first time before the age of 18 than for those who give birth at the age of 30, and the risk of breast cancer is greater for those who give birth for the first time after the age of 30 than for those who have never given birth. It is generally believed that women who have had one child are less likely to develop breast cancer than women who have not had children. It has been found that breast cancer patients tend to marry late and have fewer children. This condition is for reference only. 8. Others: It was thought that breastfeeding might have a protective and preventive effect, but in fact breastfeeding does not reduce the risk of breast cancer. In women with other cancers (uterine, colon, ovarian, etc.), the chance of breast cancer is approximately one times greater than in the general population. Although there are so many risk factors for breast cancer, most women actually have at least 1 secondary risk factor; and the number of cases in which risk factors can be used to explain breast cancer is only about 1/4 of the total number of cases.