I also had bilateral mastectomies and took Tamoxifen afterwards to prevent a recurrence. Both oncologists I consulted told me that no mastectomy removes 100% of the breast tissue in the body, some always remains. Theoretically it is possible to develop breast cancer in this remaining tissue.
Dear millerpuryear: It is unusual to prescribe arimidex prior to surgery, especially if the hormone status of the tumor is unknown. Once the tumor is removed, it should be tested for estrogen and progesterone receptors. If these are positive, it means that estrogen may feed the growth of the cancer or cancer cells. This is the reason to take arimidex or tamoxifen or another anti-estrogen drug to stop the growth ability of any possible stray cancer cells. If the tumor is estrogen/progesterone receptor negative, there would be little or no reason to take these types of medications.