One of the most obvious reasons a double mastectomy may be necessary is when cancer is affecting both of breasts. The doctor may recommend a bilateral mastectomy be performed to eliminate the cancerous cells. However, there are other treatment options available for one or both of the breasts if the cancer is not widely spread and if the patient is not at high risk for developing breast cancer again.
A double mastectomy is sometimes performed even when only one of the breasts is affected by cancer. In these cases, the decision to remove the tissue from both breasts as opposed to only the one containing cancer cells is largely preventative. Some patients may even have the preventative mastectomy in the absence of cancer. This may include patients who carry a gene mutation that makes them high risk for developing breast cancer or patients who have a strong family history of breast cancer and want to take measures to avoid developing breast cancer in the future.