Traditional treatments for breast cancer often involve chemotherapy,
radiation or hormonal therapy to halt the spread of the cancer, coupled with
a removal of the affected tissue areas. The old traditional removal method is
called a "radical mastectomy" or "modified radical mastectomy,"
and involves removal of the entire affected breast, the lymph nodes under the
arm, and sometimes the lining over the chest muscles as well. In recent years,
new techniques have been used in which it is not necessary to remove the
entire breast (called a lumpectomy or partial mastectomy.)
Following a mastectomy, there are several options available to a woman; she can live without a breast, have breast reconstruction surgery, or she can wear a prosthesis. Choosing which alternative(s) is best is really up to you and how you feel. Please note that these are not the ONLY options, just some of the more common ones - you should always consult with your doctor about treatment options.
Questions about the details and ramifications of breast reconstruction and living with a single breast are addressed by the resources listed in the previous question (7) with more sensitivity and thoroughness than I could ever hope to offer here and I recommend these resources highly.