Most testing labs use a special staining process that makes the hormone receptors show up in a sample of breast cancer tissue. The test is called an immunohistochemical staining assay, or ImmunoHistoChemistry (IHC). Not all labs use the same method for analyzing the results of the test, and they do not have to report the results in exactly the same way. So you may see any of the following on your pathology report:
- A percentage that tells you how many cells out of 100 stain positive for hormone receptors. You will see a number between 0% (none have receptors) and 100% (all have receptors).
- An Allred score between 0 and 8. This scoring system is named for the doctor who developed it. The system looks at what percentage of cells test positive for hormone receptors, along with how well the receptors show up after staining (this is called “intensity”). This information is then combined to score the sample on a scale from 0 to 8. The higher the score, the more receptors were found and the easier they were to see in the sample.
- The word “positive” or “negative.”
Keep in mind that a test should be done for both estrogen receptors and progesterone receptors. If your result is reported as just the word “positive” or “negative,” ask your doctor for a more definite percentage, rating, or other number. You also can ask about how these more precise results might influence treatment decisions for your particular situation.
Different labs have different cutoff points for calling the cancer either “hormone-receptor-positive” or “hormone-receptor-negative.” For example, if less than 10% of your cells — or fewer than 1 in 10 — stain positive, one lab might call this a negative result. Another lab might consider this positive, even though it is a low result. Research studies have shown that even cancers with low numbers of hormone receptors may respond to hormonal therapy.
A score of “0” generally means that hormonal therapy will not be helpful in treating the breast cancer. When the score is 0, the cancer is called hormone-receptor-negative.
Sometimes, a report will come back from the laboratory saying that the hormone status is “unknown.” If you receive a result of “unknown,” ask your doctor what this means, and ask what further steps should be taken to determine your hormone receptor status.
Talk with your doctor to make sure that your test is done by a laboratory with a great deal of experience in hormone receptor testing. The more tests the lab does, the more accurate your results are likely to be. If you receive a negative test result, ask for a complete explanation as to why the cancer is considered hormone-receptor-negative. Talk to your doctor about the criteria that were used to determine the negative status and whether the results should be looked at again.
What do the results mean?
After testing, your doctor will be able to tell you which of the following categories best describes the breast cancer. Most breast cancers are hormone-receptor-positive.
- ER+: About 80% of breast cancers are estrogen-receptor positive.
- ER+/PR+: About 65% of estrogen-receptor-positive breast cancers are also progesterone-receptor-positive. This means that the cells have receptors for both hormones, which could be supporting the growth of the breast cancer.
- ER+/PR-: About 13% of breast cancers are estrogen-receptor-positive and progesterone-receptor-negative. This means that estrogen, but not progesterone, may be supporting the growth and spread of the cancer cells.
- ER-/PR+: About 2% of breast cancers are estrogen-receptor-negative and progesterone-receptor-positive. This means that the hormone progesterone is likely to support the growth of this cancer. Only a small number of breast cancers test negative for estrogen receptors but positive for progesterone receptors. More research is needed to better understand progesterone-receptor-positive breast cancers.
- ER-/PR-: If the breast cancer cells do not have receptors for either hormone, the cancer is considered estrogen-receptor-negative and progesterone-receptor-negative (or “hormone-receptor-negative”). About 25% of breast cancers fit into this category.
Any positive test result — whether just for estrogen receptors, just for progesterone receptors, or both — means that the breast cancer is considered “hormone-receptor-positive.” Hormonal therapy may help to slow or stop the growth of hormone-receptor-positive breast cancers by lowering your body’s estrogen levels or blocking the effects of estrogen. These medications also may reduce the risk that the cancer will come back (recur).
If your cell sample tests positive, your doctor usually will prescribe some form of hormonal therapy at some point in your treatment plan. If the breast cancer is hormone receptor-negative (ER- and PR-), your doctor is unlikely to recommend hormonal therapy. But remember that many other effective treatments are available.