Breast cancer is a malignant tumor that is more prevalent in women and rare in men. Its incidence varies significantly around the world, with the United States and Northern Europe being the most prevalent regions, followed by Eastern and Southern Europe and South America, and Asia being the least prevalent. However, since the 1970s, the incidence has been increasing in Asia, which used to be a low incidence region. China was a low incidence area for breast cancer, but in recent years there has been a significant increase. According to the epidemiological data of a few major cities, the incidence rate of female breast cancer in Tianjin (the world standardized rate) was 18.2 per 100,000 people between 1981 and 1982, and it was as high as 24.94 per 100,000 people between 1988 and 1992, an increase of 37%, and it has risen to the second place among female malignant tumors. The incidence rate in Shanghai is higher than that in Tianjin, which was 18.8 per 100,000 people in 1981 and rose to 46 in 1997, up 244.7%, ranking the top of female malignant tumors. How to prevent breast cancer? First of all, we need to understand what are the risk factors for breast cancer in order to prescribe the right medicine. Although the etiology of breast cancer is complex and the pathogenesis is not really understood, some etiological studies have shown that some relevant factors are related to the development of breast cancer. 1. There is a correlation between family history and breast cancer. As early as 1974, Anderson et al. noted that women with first-degree relatives with breast cancer were two to three times more likely to develop breast cancer than those without a family history. The relative risk was up to 9 times higher if the first-degree relative had bilateral breast cancer before menopause. A survey conducted in Shanghai in 1988-1989 showed that the relative risk of breast cancer among women with a family history of breast cancer was 4.5, which shows that family history is an important risk factor. 2. Reproductive factors: Since breast cells undergo physiological proliferation due to the cyclical changes of hormone levels in the body and the increase of hormone levels in the body during pregnancy, the occurrence of breast cancer is related to age of menarche, age of menopause, menstrual cycle, number of births, history of breastfeeding and marital status. The risk of breast cancer is higher in unmarried women, early menarche, late menopause, short menstrual cycle, less frequent menstruation and not breastfeeding. On the contrary, the risk is lower. 3. Sex hormone level is also one of the causes of breast cancer. Studies have shown that breast cancer is very rare in women younger than 20 years old, and it is not common in women younger than 30 years old. From the age of 35, the incidence of breast cancer increases year by year and this increase in incidence continues almost throughout a woman’s life. Between the ages of 45 and 50, the increase tapers off slightly and then rises steeply again. The intake of exogenous estrogen will greatly increase the incidence of breast cancer, such as: oral estrogen-containing drugs, transdermal absorption of estrogen in volumizing lotions, and oral contraceptives. 4. Nutritious diet, fatty and high-calorie diet, and alcohol consumption all increase the risk of breast cancer. 5. Previous history of benign breast tumors. Other factors include radiation, viruses, chemical stimulation and certain diseases such as diabetes can also cause an increased incidence of breast cancer.