Kate, these are independent conditions.  The BRCA 1 and 2 mutations mean that a person is much more likely to develop breast cancer but does not predict whether the cancer will be estrogen receptor positive or negative.  Nor does it relate to whether the cancer will be Her 2 positive.  Once a person has been diagnosed with breast cancer, the two main reasons to do the genetic testing are to find out if the person's family members may have a higher risk for developing breast cancer and to find out whether there is a higher risk of developing another breast cancer in the other breast.  Having the BRCA mutation may also affect a person's risk for ovarian cancer.