If you have breast cancer, your doctor may order more lab tests to help figure out how serious it is. The hormone receptor test and the HER2/neu test are the two lab tests that are done most often. The results of these tests can help you figure out which cancer treatments might work best for you.
Trying to find hormone receptors on the tumor cells.
A hormone receptor is a special protein that is either on the outside of a cell or inside of it. The female hormones estrogen and progesterone, which flow through the blood, bind to the receptor. Once the cell is bound, the hormone tells it to start growing and making more copies.
Many breast cancer tumors, and often a lot of them, have hormone receptors. When there are hormone receptors, estrogen and/or progesterone can help the cancer grow. Hormone therapy, which is different from hormone replacement therapy, works well for many of these hormone-dependent cancers (HRT). If neither estrogen receptors (ER) nor progesterone receptors (PR) are present, the cancer is called "hormone-receptor-negative," and hormone therapy is probably not going to help. Your medical team and treatment plan can benefit from knowing if the cancer cells have hormone receptors.
Who Needs to Be Tested for Hormone Receptors?
In general, testing for hormone receptors is recommended for all types of breast cancer, including DCIS. If your doctor orders this test, you may need to stop taking any hormones for a while before a sample of breast tissue can be taken. The sample is usually taken from a biopsy, but the test can also be done on tissue that was taken out during a lumpectomy or mastectomy. It is, however, a standard of care to get these kinds of pathology results from a biopsy.
What's the point of the test?
To check for hormone receptors, the testing lab usually uses a special staining process on a sample of breast tissue. This test is called a "immunohistochemical staining assay" or "ImmunoHistoChemistry (IHC)" in the scientific world. The results will be written up in a report that will be given to your doctor. If the cancer is called "estrogen-receptor-positive" (ER+), it means that the cells of the cancer have receptors for the hormone estrogen. That means that estrogen is most likely telling the cancer cells to grow. Hormone receptors are found in about two out of every three breast cancers.
If the cancer is progesterone-receptor positive (PR+), its cells have progesterone receptors. The cancer could then grow faster because of this hormone.
A good prognostic factor is that the cancer cells are estrogen and/or progesterone receptor-positive (hormone positive). This usually means that the prognosis will be better.
What do the results of a test for hormones show?
Patients with breast cancer who test positive for both estrogen receptors and progesterone receptors have a better chance than average of living and getting better than those who don't have either receptor. Also, hormone therapy works better the more receptors a person has and the stronger their reaction. Patients who only have one type of receptor may still benefit from this type of treatment, but probably not as much. As was already said, hormone therapy probably won't help if the cancer is both ER-negative and PR-negative. Here are some typical responses to hormone therapy:
Positive for ER and PR: 75-80% of ER positive and PR negative: 40–50% of negative ERs and positive PRs: 25–30% negative ER and negative PR: 10% or less
The HER2/neu test is similar to the hormone receptor test in that it looks for a certain kind of protein that is found in some cancer cells and the gene that makes it. This gene is called human epidermal growth factor receptor 2 (HER2), and it makes HER2 proteins. Breast cells have receptors for these proteins.
In a way, genes are like a recipe for how many and what kinds of proteins a cell needs to stay healthy and work right. Certain genes and the proteins they make can affect how breast cancer grows and how it responds to different treatments.
What is a HER2 receptor? How does it relate to breast cancer?
Proteins called HER2 receptors help control how a breast cell grows, divides, and fixes itself. But the HER2 gene isn't working right in about a quarter of all breast cancer patients. HER2 gene amplification is the process by which it makes too many copies of itself. Then, the extra genes tell the cells to make too many HER2 receptors. This is called "HER2 protein overexpression." The end result is that the cells in the breast grow and divide out of control.
The HER2/neu test can tell if the sample is normal or if it has too much of the HER2/neu protein or too many copies of the gene for it. If you have had invasive breast cancer or breast cancer that has come back, your doctor may suggest this test. It will help your oncology team figure out your prognosis, what the tumor looks like, and how aggressive it is likely to be. It will also help them figure out the best way to treat you.
The hormone receptor test is often ordered along with this one. Most of the time, breast cancer tissue from a biopsy or a tumor taken out during a mastectomy is used. The pathology results for this test can take up to a week to come back, but it usually only takes a day or two to find out if the cells are cancerous.
What will I learn from the HER2/neu results?
There are four tests for HER2, and the results may show up on your pathology report, which may take a few weeks to come back.
The IHC test is the first one. IHC stands for "ImmunoHistoChemistry." It checks to see if the cancerous cells have too much HER2 protein. If the result is 0 or 1+, there isn't too much HER2 protein. If the result is 2+ or 3+, the cells have too much HER2 protein.
The last three tests look at how many copies of the HER2 gene are in the cells. Among these tests are:
The FISH test (which stands for "Fluorescence In Situ Hybridization") looks for the presence of certain genes.
The SPoT-Light HER2 CISH (Subtraction Probe Technology Chromogenic In Situ Hybridization) test checks for the presence of HER2.
The Inform HER2 Dual ISH test ("Inform Dual In Situ Hybridization") checks for the presence of two types of HER2.
For these three tests, there are only two possible results: positive, which means that the number of HER2 genes is too high, or negative, which means that the number of HER2 genes is not too high.
In the pathology report, breast cancers with overexpression of the HER2 protein and amplification of the HER2 gene are called "HER2-positive." This kind of breast cancer tends to grow faster, spread to other parts of the body more easily, and come back more often than HER2-negative breast cancer.
Checking the blood for HER2/neu
When there isn't enough tumor tissue to do the test, a blood sample is sometimes taken from the patient's arm to get similar information. This blood test is called a "serum HER2/neu test," and it can be done when cancer is first found or to check on how well treatment is working. If the level of serum HER2/neu is higher than 15ng/mL at first but then goes down, it's likely that the treatment is working. But if the serum level stays high, it means that the treatment is not working. If the serum level goes down, but then goes back up when tested later, this could mean that the cancer is coming back.
When all three tests come back negative for hormone receptors (progesterone and estrogen) and HER2, the person may have triple-negative breast cancer.