What does HER Status mean?

Some women have breast tumors with higher levels of a protein known as HER2. These cancers are called HER2-positive breast cancers. Ask your doctor about your HER2 status and what it means for you.⁠
What is HER2 and what does it mean?⁠

HER2 is a protein that helps breast cancer cells grow quickly. Breast cancer cells with higher than normal levels of HER2 are called HER2-positive. These cancers tend to grow and spread faster than breast cancers that are HER2-negative, but are much more likely to respond to treatment with drugs that target the HER2 protein.⁠

All invasive breast cancers should be tested for HER2 either on the biopsy sample or when the tumor is removed with surgery.⁠

What do the test results mean?⁠

The results of HER2 testing will guide you and your cancer care team in making the best treatment decisions.⁠

It is not clear if one test is more accurate than the other, but FISH is more expensive and takes longer to get the results. Often the IHC test is done first.⁠

If the IHC result is 0 or 1+, the cancer is considered HER2-negative. These cancers do not respond to treatment with drugs that target HER2.⁠
If the IHC result is 3+, the cancer is HER2-positive. These cancers are usually treated with drugs that target HER2.⁠
If the IHC result is 2+, the HER2 status of the tumor is not clear and is called “equivocal.” This means that the HER2 status needs to be tested with FISH to clarify the result.⁠

Triple-negative breast tumors don’t have too much HER2 and also don’t have estrogen or progesterone receptors. They are HER2-, ER-, and PR-negative. Hormone therapy and drugs that target HER2 are not helpful in treating these cancers. See Triple-negative Breast Cancer to learn more.⁠

Triple-positive breast tumors are HER2-, ER-, and PR-positive. These cancers are treated with hormone drugs as well as drugs that target HER2.⁠