Many patients may ask, “Why do I have breast cancer? I usually take good care of my health, right? I have regular checkups? I’m careful about what I eat. However, we regret to tell you that we do not know the direct cause of breast cancer so far. We only know of the following risk factors. Genetic factors: Women who have breast cancer in their family have a higher risk of developing breast cancer than the general population. For example, if your mother, sister, sister or daughter is a breast cancer patient, your risk of breast cancer is about 2-3 times higher than normal; people with BRCA1 and BRCA2 genes, patients with ovarian cancer and endometrial cancer. Fertility factors: The risk of breast cancer is higher for women who have had their first menstrual period earlier than 12 years, menopause later than 55 years, have their first child at an age older than 30 years, or have never had a child. Environmental factors: Immigrants to countries with a high incidence of breast cancer, long-term use of birth control pills and estrogen-containing foods, poor dietary habits (long-term alcohol consumption, high animal fat diet, etc.), chronic stress and mood disorders, etc. Other factors: including postmenopausal obesity, high-fat diet, other breast diseases (e.g. atypical breast hyperplasia, breast cancer in one breast), etc.