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Does this test have other names?

Human epidermal growth factor receptor 2, ERBB2, HER2

What is this test?

This is a tissue test to check if a certain protein involved in cell growth (HER2/neu) is present in some types of cancer cells. Some cancers, especially invasive breast cancers, have more HER2/neu protein than normal. About 20% of breast cancers have high numbers of these proteins on their cell surfaces.

If you have a biopsy that shows you have breast cancer or you have surgery for breast cancer, this test will be done on the breast tissue that has been removed to check for HER2/neu. Learning your HER2/neu status helps your healthcare providers plan the best treatment for you.

HER2/neu can also be measured by a blood test. But it's not done very often.

Why do I need this test?

If you are diagnosed with breast cancer, you may have this test to find out more about your condition. If you are being treated for breast cancer with a cancer medicine, this test can help your healthcare provider find out how well you are responding to treatment.

What other tests might I have along with this test?

If your HER2/neu is being measured after biopsy or surgery, your healthcare provider may order other tests on breast cancer cells to learn more about your cancer. If these other tests find receptors for the female hormones estrogen and progesterone, it means you may respond better to some types of cancer medicines.

What do my test results mean?

Test results may vary depending on your age, gender, health history, and other things. Your test results may be different depending on the lab used. They may not mean you have a problem. Ask your healthcare provider what your test results mean for you.

HER2/neu on cancer cells is measured in 2 ways.

  • Immunohistochemistry (IHC) testing checks for this protein on the surface of cancer cells.

  • Fluorescence in situ hybridization (FISH) tests for the genes that direct the cell to make HER2/neu protein.

If your cancer is HER2/neu positive, you may respond to a specific medicine that targets HER2/neu receptors.

Results for IHC:

  • A score of 0 or +1 means your tumor is HER2 negative.

  • A score of +2 means the results are unclear and FISH testing should be done.

  • A score of +3 means the tumor is HER2 positive.

FISH results are positive or negative.

If you are having the blood test, HER2/neu is measured in nanograms per milliliter (ng/mL).

How is this test done?

The tissue sample test is done on the breast tissue that was removed in a biopsy or cancer surgery.

The test may also require a blood sample, which is drawn through a needle from a vein in your arm.

Does this test pose any risks?

The tissue sample does not pose any risk aside from the risks of the surgery.

Taking a blood sample with a needle carries risks that include bleeding, infection, bruising, or feeling dizzy. When the needle pricks your arm, you may feel a slight stinging sensation or pain. Afterward, the site may be slightly sore.

What might affect my test results?

Only the type of cancer you have and the type of treatment you receive can affect your results.

How do I get ready for this test?

You don't need to prepare for this test. Be sure your healthcare provider knows about all the medicines, herbs, vitamins, and supplements you are taking. This includes medicines that don't need a prescription and any illegal drugs you may use. 

Online Medical Reviewer: Chad Haldeman-Englert MD
Online Medical Reviewer: Raymond Kent Turley BSN MSN RN
Online Medical Reviewer: Raymond Turley Jr PA-C
Date Last Reviewed: 3/1/2022
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