HER2 Tumor Marker Test
Reviewed
Also called: Human epidermal growth factor receptor 2, ERBB2 amplification, HER2 overexpression, HER2/neu tests
HER2 tumor marker tests look for the tumor marker called human epidermal growth factor receptor 2 (HER2). Tumor markers are substances made by cancer cells.
Specimen: Tumor tissue
Why this test may be ordered
- To determine if breast, stomach, or esophageal cancer is HER2 positive or negative
- To guide whether HER2 targeted therapy may be effective
- To assess how fast cancer may grow and likelihood of spread
- To test recurrent or metastatic cancer even if initial tumor was tested
Preparation and collection
Preparations for your test depend on how your tissue sample will be taken. Ask your provider how to prepare for your test. If you are getting medicine to relax or sleep during the procedure, you will probably need to fast (not eat or drink) for several hours before surgery. You will also need to have someone take you home, because you may be sleepy after the procedure.
Most HER2 testing uses a sample of tumor tissue. The tissue will be removed during a procedure called a biopsy. The type of biopsy you have depends on where the tumor is located.
Risks depend on how your tissue sample is taken. In general, if you are having a biopsy, you may have a little bruising or bleeding where the tissue was removed. Ask your provider to explain any risks from a biopsy.
Understanding results
The results of HER2 tumor marker tests are reported differently, depending on the type of test you had.
- IHC score 0 or 1+: 0 (zero) or 1+ means that your cancer cells don't have high levels of HER2 protein. In breast cancer, these results are considered HER2-negative. Limitation: However, some breast cancers with these results may have low levels of HER2 (sometimes called HER2-ultralow or HER2-low) that your provider can treat with certain newer medicines. Next step: Your provider will consider your HER2 results along with other information about your cancer when choosing treatment.
- IHC score 2+ (equivocal): 2+ means that the amount of HER2 protein is borderline. This may be reported as "equivocal," which means the test result is not clear. Limitation: The results of HER2 tumor marker tests are reported differently, depending on the type of test you had. Next step: You may need a different type of test, such as a FISH test, to see if your cancer is HER2 positive.
- IHC score 3+: 3+ means that your cancer cells have high levels of HER2 protein. Your cancer is HER2 positive. Limitation: Your provider will consider your HER2 results along with other information about your cancer when choosing treatment. Next step: Talk with your provider to learn what your results mean.
- FISH: HER2 negative: HER2 negative, which means the test did not find enough extra copies of the HER2 gene for the cancer to be HER2-positive. Limitation: However, like with IHC testing, HER2 negative results don't necessarily mean that the cancer has no HER2 protein. Next step: Talk with your provider to learn what your results mean.
- FISH: HER2 positive: HER2 positive, which means the test found enough extra copies of the HER2 gene for the cancer to be HER2-positive. HER2 targeted therapy will likely be useful in treating your cancer. Limitation: The results of HER2 tumor marker tests are reported differently, depending on the type of test you had. Next step: Your provider will consider your HER2 results along with other information about your cancer when choosing treatment.
- Blood tests for HER2 are not recommended because it is not clear how blood test results can plan cancer treatment.
- Cancer cells can change over time, so retesting may be needed for recurrent or metastatic disease even if the first tumor was tested.
- IHC score 2+ is borderline (equivocal) and requires additional testing, such as FISH, for a definitive result.
What to do next
Your provider will consider your HER2 results along with other information about your cancer when choosing treatment. Talk with your provider to learn what your results mean.
- What type of HER2 test was performed on my sample (IHC or FISH)?
- What does my HER2 result mean for my cancer treatment options?
- If my result is equivocal, what additional tests are needed and how long will they take?
- Should I have my tumor retested if my cancer comes back or spreads?
- Are there any clinical trials for HER2-targeted therapies that I might be eligible for?
Evidence source
Source: U.S. National Library of Medicine (MedlinePlus). Practices and reference ranges may differ in your country.