Breast cancer cells that have receptors on their surface to attach to and grow from the hormones estrogen and/or progesterone are considered ‘hormone positive’. Certain drugs have been developed that either block the hormone (estrogen) from attaching to the cancer cell, or prevent the body from making estrogen in the first place. These drugs are taken for several years to help keep the cancer from coming back or to keep from growing if
Some good general information regarding hormone therapy can be found here.