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    What Is HER2-Positive Breast Cancer?

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    If your breast cancer is “HER2-positive,” it’s more aggressive than other types of breast tumors, but treatments can help.

    About 1 of every 5 of breast cancers are HER2-positive. That means the cancer cells have more of a protein called HER2, human epidermal growth factor receptor 2. It causes these cells to grow and spread faster than the ones with normal levels of the protein.

    You’ll work with your doctor to review the treatment options and come up with a plan that's best for you.


    Doctors don’t know the exact causes of breast cancer. Experts think it may be a combination of things, including your genes, environment, and lifestyle.

    You can't inherit a bad copy of the HER2 gene from a parent, and you won’t pass it on to your children.


    The most common warning sign of any type of breast cancer is a lump in your breast that feels different from the area around it. That’s true for the HER2-positive type, too.

    Other symptoms may include:

    • Breast swelling
    • A change in its shape
    • Skin irritation or dimpling
    • Pain in the breast or nipple
    • Redness or thickness of the nipple or breast skin
    • Discharge from the nipple (not breast milk)

    You may have noticed a difference in your breasts during a self-exam. Or you may have had a mammogram that showed a growth.


    When you find out that you have breast cancer, your doctor will check to see if yours is HER2-positive. She'll probably give you one or more of these tests:

    The IHC test uses certain antibodies that identify the HER2 protein in a sample of breast cancer tissue. If there is a lot of it, the cells change color in the sample.

    These tests see if there are too many HER2 genes in the cancer cells:

    The FISH test uses fluorescent pieces of DNA that stick to the HER2 gene in cells, which can then be counted under a microscope.

    The SPOT-Light HER2 CISH and the Inform HER2 Dual ISH tests use stains that color HER2 genes in a tissue sample, so that they can be counted under a microscope.

    Sometimes the results of a single test aren't clear. If that happens, your doctor may order another type.

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