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    Prognostic Factors
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    Hormone Therapy Video
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    Research Fast Facts: HER2-Positive Breast Cancer Fact Sheet

    Hormone receptor status

    Hormone receptor status is a main factor in planning breast cancer treatment.

    Some breast cancer cells grow with the help of estrogen and/or progesterone (female hormones produced in the body). These cancer cells have special proteins inside, called hormone receptors. When hormones attach to hormone receptors, the cancer cells with these receptors grow.

    A pathologist determines the hormone receptor status by testing the tumor tissue removed during a biopsy.

    • Hormone receptor-positive (estrogen receptor-positive (ER-positive)/progesterone receptor-positive (PR-positive)) breast cancers have many hormone receptors.
    • Hormone receptor-negative (estrogen receptor-negative (ER-negative)/progesterone receptor-negative (PR- negative)) breast cancers have few or no hormone receptors.

    Most (about two out of three) breast cancers are hormone receptor-positive [27].

    Hormone receptor status and hormone therapy

    Hormone receptor-positive breast cancers can be treated with hormone therapies. These include tamoxifen and the aromatase inhibitors, anastrozole (Arimidex), letrozole (Femara) or exemestane (Aromasin).

    Hormone receptor-negative breast cancers are not treated with hormone therapies because they do not have hormone receptors.

    Estrogen receptor status and progesterone receptor status

    Breast cancers that are ER-positive also tend to be PR-positive. And, cancers that are ER-negative tend to be PR-negative.

    Sometimes, a breast cancer is positive for estrogen receptors, but negative for progesterone receptors. Because current hormone therapies are designed to treat ER-positive cancers, these cases are treated the same as breast cancers that are positive for both hormone receptors.

    How do hormone therapies work?

    Hormone therapies slow or stop the growth of hormone receptor-positive tumors by preventing the cancer cells from getting the hormones they need to grow. They do this in a few ways.

    Some hormone therapies, like the drug tamoxifen, attach to the receptor in the cancer cell and block estrogen from attaching to the receptor.

    Other therapies, like aromatase inhibitors, lower the level of estrogen in the body so the cancer cells cannot get the estrogen they need to grow.

    Hormone receptor status and prognosis

    Hormone receptor status is also related to the chance of breast cancer recurrence.

    Hormone receptor-positive tumors have a slightly lower chance of breast cancer recurrence than hormone receptor-negative tumors in the first five years after diagnosis. However, after five years, this difference begins to decrease and eventually goes away [9,28].

    Learn more about hormone therapies.  

    Learn about hormone receptor status information on a pathology report.


    For a summary of research studies on hormone receptor status and survival, visit the Breast Cancer Research Studies section.

    HER2 status

    HER2 (human epidermal growth factor receptor 2) is a protein that appears on the surface of some breast cancer cells. It may also be called HER2/neu or ErbB2. This protein is an important part of the pathway for cell growth and survival.

    • HER2-positive (HER2-positive) breast cancers have a lot of HER2 protein.
    • HER2-negative (HER2-negative) breast cancers have little or no HER2 protein.

    About 20 percent of all breast cancers are HER2-positive (you also may hear the term “HER2 over-expression”) [29-30].

    HER2 status helps guide treatment.

    HER2-positive cancers and targeted therapy

    HER2-positive breast cancers can benefit from anti-HER2 drugs, such as trastuzumab (Herceptin), which directly target the HER2 receptor [9]. Trastuzumab and other anti-HER2 targeted therapies are not used for HER2-negative cancers.

    Learn about trastuzumab in the treatment of early and locally advanced breast cancer.

    Learn about trastuzumab, lapatinib and other targeted therapies in the treatment of metastatic breast cancer.

    Learn about emerging targeted therapies for HER2-positive metastatic breast cancer.

    Testing for HER2 status

    All tumors should be tested for HER2 status.

    The two common ways to determine HER2 status are:

    1. Immunohistochemistry (IHC) testing detects the number of HER2 protein receptors in the cancer cells.
    2. Fluorescence in situ hybridization (FISH) testing detects the number of HER2 genes in the cancer cells.

    Learn about HER2 status information on a pathology report.

    Proliferation rate

    How fast a tumor grows (known as proliferation rate) can help show how aggressive a tumor is and how likely it is to spread to other parts of the body.

    Tumors with a high proliferation rate (those that are growing fast) often have a poorer prognosis than those with a low proliferation rate.

    Proliferation rate is an important predictor of prognosis and whether or not a tumor will respond to chemotherapy. However, there are issues related to its measurement. So, while some health care providers may use it to help guide treatment options, others do not.


    The Ki-67 test is a common way to measure proliferation rate. When cells are growing and dividing (proliferating), they make proteins called proliferation antigens. By counting the number of cells with these antigens, a pathologist can determine a tumor's proliferation rate.

    The antibody to Ki-67 attaches itself to the proliferation antigen. The more cells the Ki-67 antibody attaches to in a tissue sample, the more likely the tumor cells are to grow and divide rapidly.

    The result of this test is reported as the percentage of Ki-67-positive cells. It shows whether a low, moderate or high proportion of cancer cells are in the process of dividing.

    Learn about proliferation rate information on a pathology report.

    Updated 10/14/15

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