Your pathology report will include the results of a hormone receptor assay, a test that tells you whether or not the breast cancer cells have receptors for the hormones estrogen and progesterone. Hormone receptors are proteins — found in and on breast cells — that pick up hormone signals telling the cells to grow.
A cancer is called estrogen-receptor-positive (or ER+) if it has receptors for estrogen. This suggests that the cancer cells, like normal breast cells, may receive signals from estrogen that could promote their growth. The cancer is progesterone-receptor-positive (PR+) if it has progesterone receptors. Again, this means that the cancer cells may receive signals from progesterone that could promote their growth. Roughly two out of every three breast cancers test positive for hormone receptors.
Testing for hormone receptors is important because the results help you and your doctor decide whether the cancer is likely to respond to hormonal therapy or other treatments. Hormonal therapy includes medications that either (1) lower the amount of estrogen in your body or (2) block estrogen from supporting the growth and function of breast cells. If the breast cancer cells have hormone receptors, then these medications could help to slow or even stop their growth. If the cancer is hormone-receptor-negative (no receptors are present), then hormonal therapy is unlikely to work. You and your doctor will then choose other kinds of treatment.
In this section, you can read more about:
- Understanding Hormone Receptors and What They Do
- How to Read Hormone Receptor Test Results
- Treatments for Hormone-Receptor-Positive Breast Cancer
- Treatments for Hormone-Receptor-Negative Breast Cancer
If cancer cells have receptors for these hormones, it's not necessarily a bad thing. It means that they are at least TRYING to perform the tasks of a normal breast cell. They're behaving — somewhat.