What is familial breast cancer? Among all breast cancers, 5-10% of breast cancer patients have a family history of breast cancer, such as mother-daughter or sister-sister. Such patients may have a “genetic predisposition to breast cancer”, which occurs because of specific genetic variants in the family, 80% of which are BRCA1/2 mutations, but also PTEN or P53 or other genetic variants. In families with BRCA1 mutations, the cumulative risk of developing breast cancer by age 70 is 85-90% for breast cancer and 60% for ovarian cancer. What is the purpose of genetic counseling for breast cancer? The purpose of a breast cancer genetic counseling clinic is to find out the risk of other members of the family through the misfortune of one patient, and to assist the patient in determining whether her breast cancer is familial and hereditary; if it is not a mutation-carrying family, then other women in the family do not need to worry about whether they are also at high risk of breast cancer; if unfortunately it is a mutation-carrying family, then it is necessary to determine If they are unfortunately carriers of the mutation, it is necessary to determine which female members of the family are carriers of the bad gene and those who are not, can be reassured that they are not, while those who are carriers of the bad gene will need to be treated accordingly. What are the benefits for the patient? 1. The biggest benefit is to finally know for sure if others in their family, including daughters and sisters, are at risk of breast cancer. If they are at high risk of developing the disease, they should be guided and monitored accordingly to prevent the unfortunate further threat to other members of the family. If you are a family member of a breast cancer patient, you can clarify whether you are a high-risk group or not. If you are a high-risk group, you should deal with it as soon as possible to prevent the life-threatening disease from occurring and threatening your life. If you already have breast cancer, what is the significance of diagnosing familial breast cancer? If you are a carrier of the BRCA1/2 mutation, you will be treated differently, such as no platinum-based chemotherapy, absolutely no breast conservation (because radiation therapy can induce new breast cancer), absolutely no mammography of the contralateral breast at follow-up (mammography can also cause new breast cancer due to high sensitivity to radiation), prophylactic excision of the contralateral breast is recommended because of its very high risk of breast cancer, and removal of the ovaries because of the equally high incidence of ovarian cancer, which has a high mortality rate. If you are not currently a breast cancer patient and you have a relative with breast cancer who has genetic testing and it turns out that you are also a carrier of the mutation, what is the practical implication? Because the cumulative risk of breast cancer for mutation carriers by age 70 is 85-90% for breast cancer and 60% for ovarian cancer, prophylactic mastectomy is recommended, or close follow-up under medical supervision before having children and direct removal of the ovaries after having children; the trouble is that mammography surveillance is prohibited for such individuals because of their sensitivity to radiation.