Thus, if your mother was 45 when she had breast cancer, you should have your first mammogram when you are 35. Tamoxifen is a drug that is very similar to estrogen. It binds to the sites on breast tissue cells where estrogen would bind, and therefore blocks estrogen. Because estrogen cannot bind, it cannot stimulate the breast. It has effects on other parts of the body as well.
Fibrocystic changes are very common, in fact, most American women have it.
Most women are not at an increased risk of breast cancer. There is a very small subset of women with fibrocystic tendency who are at increased risk, based upon findings at biopsy or on mammography. Most women are not at increased risk. Even for early stage disease, many physicians recommend additional systemic therapy. This might be Tamoxifen or it might be chemotherapy.