When a person is diagnosed with breast cancer, tests are then conducted to study the cancer cells. According to the National Cancer Institute, such tests are used to determine how quickly the cancer may grow and the likelihood that the cancer will spread throughout the body. These tests also may help doctors determine a course of treatment and if a patient is likely to experience a recurrence of the cancer down the road. One such test is the estrogen and progesterone receptor test, which measures the amount of estrogen and progesterone receptors in cancer tissue. The cancer may grow more quickly in patients who have more of these receptors than normal. In addition to measuring the amount of these hormones in the cancer tissue, an estrogen and progesterone test can determine if a treatment aimed at blocking estrogen and progesterone may prevent the cancer from growing.