The age of onset of breast cancer in China is mainly concentrated between 40 and 45 years old. The cause of breast cancer is related to estrogen and progesterone in the body, and its development is related to diet, obesity and genetic background. It has been found that if the mother and first generation of immediate family members develop breast cancer after menopause, then the chance of children developing breast cancer is 20% more than normal population. If a mother develops breast cancer before menopause, her children are twice as likely to develop breast cancer. If a mother has unilateral breast cancer, her children’s chance of developing breast cancer is only one time higher than normal; if a mother has bilateral breast cancer before menopause, her children’s chance of developing breast cancer is seven to eight times higher than normal, and these people often have genetic mutations, which should be highly alerted. The true cause of breast cancer is not well understood, but if a patient has a BRCA-1 gene mutation in her blood or tissues, and her children can also be found to have a BRCA-1 gene mutation, then her children are at high risk. A person with BRCA-1 genetic mutation has more than 80% chance of developing breast cancer in her lifetime, with an earlier age of onset and a higher chance of having ovarian cancer. If you have a family history of breast cancer, you may want to get genetic testing to prevent it from happening.