Does this test have other names?
ER/PR IHC testing
What is this test?
This test looks for several types of receptors on cells in a sample of breast cancer tissue.
From 60% to 75% of breast cancers depend on the hormone estrogen to grow. A few breast cancers can grow without estrogen. The cancer cells that depend on estrogen make many estrogen receptors (ER), progesterone receptors (PR), or both. These receptors grab onto the hormones that float freely in your blood and use them as fuel to help cancer grow.
Cancers that contain ERs are called ER-positive (ER+). Cancers that contain PRs are called PR-positive (PR+). Cancers with these types of receptors are called "hormone responsive" cancers.
The immunohistochemical (IHC) test also looks for cell receptors that hold onto HER2, or human epidermal growth factor type 2. HER2 is a protein that is found in excessive amounts in about 1 in 5 breast cancers. HER2-positive cancers have many receptors that hold HER2 and are more aggressive than cancers that don't have a lot of HER2.
Before your healthcare provider can figure out what type of cancer treatment is best for you, he or she must look at your tumor cells in order to know the ER, PR, and HER2 status.
To do this, your provider sends a sample of your tumor to a lab. There, a pathologist runs tests on the sample and looks at the cells under a microscope.
Why do I need this test?
You may need this test if you have breast cancer and your healthcare provider needs more information about the type of breast cancer you have.
If you have hormone-responsive cancer, you will most likely be helped by treatments that will block estrogen from attaching to the receptors or that will lower the total estrogens in your system. If you are hormone receptor-positive/HER2-negative or HER2-positive, you may be offered treatment with medicines known as targeted therapy. Targeted therapy medicines attack certain proteins or cell functions that help cancer cells grow.
What other tests might I have along with this test?
Your healthcare provider may also order other tests to help diagnose and treat your breast cancer. These tests include:
- Blood tests. A complete blood count, or CBC, will check to see whether your blood counts are normal. Chemical and enzyme tests will check to see whether your organs are working the way they should.
- Fluorescent in situ hybridization (FISH). A test that checks a sample of the tumor for genes that direct the cell to make HER2/neu protein.
- Genetic testing of the tumor sample. This test will help your healthcare provider decide whether you need chemotherapy.
- Lymph node needle biopsy. It's common for breast cancer to spread to nearby lymph nodes. If your healthcare provider feels that your lymph nodes are enlarged or different in any way, he or she will do a needle biopsy. Whether the nodes are positive for cancer will help your provider figure out or refine your treatment plan.
What do my test results mean?
Test results may vary depending on your age, gender, health history, the method used for the test, and other things. Your test results may not mean you have a problem. Ask your healthcare provider what your test results mean for you.
If your results are positive for estrogen receptors, it means you are ER+. If your results are positive for progesterone receptors, it means you are PR+. In either case, hormone or endocrine therapy will likely decrease the chance that your cancer will grow or return. If your tumor, or tissue sample, does not show hormone receptors, you are ER-negative, PR-negative, or negative for both. In that case, hormone therapy will most likely not be helpful to you.
IHC results for HER2 are reported as 0, 1+, 2+, or 3+. A score of 0, 1+, means the tumor is HER2-negative. A score of 2+ means the results are unclear and another test is needed such as FISH. A score of 3+ means the tumor is HER2-positive.
Your healthcare provider will review your results together to figure out the best therapy for you. It could be hormone therapy, chemotherapy, or targeted therapy.