Breast cancer genes BRCA1 and BRCA2 are tumor suppressor genes whose mutations significantly increase the likelihood of developing particular types of epithelial malignancies, namely breast and ovarian cancer.
BRCA1 associated breast cancers are generally what we call triple negative, estrogen receptor negative, progesterone receptor negative, and HER2 new negative. Whereas BRCA2 associated breast cancers are generally estrogen receptor positive. Not always, but more often than not.
Genetic testing involves first searching for a gene mutation. The genes most commonly tested are BRCA1 and BRCA2. After genetic counselling, a sample of blood is usually taken from a woman in the family who has developed breast cancer or ovarian cancer. The DNA is 'searched' for a gene fault.