I've read about women with breast cancer in one breast choosing to have both removed. why would you do that?

Multiple reasons: For many it is a personal decision, they may feel there body failed them and they don't "need them anymore". For those with a gene mutation that puts them at high risk of getting another breast cancer it can substantially reduce their risk. If someone needs a mastectomy on one side they may opt to have both removed for symmetry.

Several reasons: 1. To avoid getting a second cancer in the healthy breast down the road 2. Because she has a brca1/2 mutation which puts her at higher risk for a second breast cancer 3. To have breast reconstruction done on both breasts at the same time 4. To avoid the anxiety and nuisance of mammograms and biopsies in the future.

Risk: This is a decision based on risk. If after counseling, the risk of a future breast cancer is increased due to family history, personal history, or genetic testing, sometimes a prophylactic mastectomy is recommended. Currently it is felt that this is an all too common practice amongst average risk patients.