Choosing to have a mastectomy can be a very emotional and difficult decision for many women. For women considering mastectomy of a breast affected by cancer, the question often comes up as to what should be done with the other breast. You may elect to have one breast (unilateral mastectomy) or both breasts removed (bilateral mastectomy). Some women with breast cancer in one breast will choose to have the opposite healthy breast removed in what is called a "contralateral prophylactic mastectomy" (CPM).