Tumor Characteristics
Hormone receptor status
Estrogen and progesterone are female hormones produced in the body. Some breast cancer cells need estrogen and/or progesterone to grow. 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. All breast cancers are tested for hormone receptor status.
- Hormone receptor-positive tumors are estrogen receptor-positive (ER-positive) and progesterone receptor-positive (PR-positive). These tumors express hormone receptors. This means they have a lot of hormone receptors.
- Hormone receptor-negative tumors are estrogen receptor-negative (ER-negative) and progesterone receptor-negative (PR-negative). These tumors do not express hormone receptors. This means they have few or no hormone receptors.
About 70% to 80% of newly diagnosed breast cancers are hormone receptor-positive [17,48].
Hormone receptor status is part of breast cancer staging and helps guide your treatment.
You may hear the term “biomarker” to describe hormone receptors. A biomarker is any molecule in your body (here, in the breast cancer tissue removed during surgery) that can be measured and gives information about your health. In this case, hormone receptor status gives information about your breast cancer.
If your breast cancer is ER-positive, PR-positive and HER2-positive, it may be called triple positive breast cancer.
If your breast cancer is ER-negative, PR-negative and HER2-negative, it may be called triple negative breast cancer.
Learn about hormone receptor status information on a pathology report.
Hormone receptor status and hormone therapy
Hormone receptor-positive breast cancers can be treated with hormone therapies (also called endocrine therapies).
Hormone therapy drugs include tamoxifen and the aromatase inhibitors anastrozole (Arimidex), letrozole (Femara) and exemestane (Aromasin). Ovarian suppression, with surgery or drug therapy, is also a hormone therapy.
Hormone receptor-negative breast cancers are not treated with hormone therapies because they don’t have hormone receptors.
Learn about hormone therapy for the treatment of early and locally advanced breast cancers.
Learn about hormone therapy for the treatment of metastatic breast cancers.
Estrogen receptor status and progesterone receptor status
Breast cancers that are ER-positive tend to be PR-positive. And cancers that are ER-negative tend to be PR-negative.
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 work in a few ways:
- Some hormone therapies, such as tamoxifen, attach to the hormone receptor in the cancer cell and block estrogen from attaching to the hormone receptor.
- Some hormone therapies, such as aromatase inhibitors and ovarian suppression, lower the level of estrogen in the body so the cancer cells can’t get the estrogen they need to grow.
Learn about hormone therapy for the treatment of early and locally advanced breast cancers.
Learn about hormone therapy for the treatment of metastatic breast cancers.
Watch our video about how the estrogen receptor causes the growth of some breast tumors and how hormone therapies put a stop to it.
Hormone receptor status and recurrence after treatment for early breast cancer
Hormone receptor status is related to the risk of breast cancer recurrence.
Hormone receptor-positive tumors have a slightly lower risk of breast cancer recurrence than hormone receptor-negative tumors in the first 5 years after diagnosis [12]. So, in the first 5 years after diagnosis, women with hormone receptor-positive cancers tend to have better breast cancer survival than women with hormone receptor-negative cancers [12,32].
After about 5 years, this difference begins to decrease [12,35]. Over time, the risk of recurrence for hormone receptor-negative breast cancers becomes lower than for hormone receptor-positive cancers [12,35]. Hormone receptor-positive breast cancers can recur more than 10 years after diagnosis, while such late recurrences are rare for hormone receptor-negative cancers [35].
| 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.
The HER2 protein is an important part of the pathway for cell growth and survival.
All breast cancers are tested for HER2 status.
You may hear the term “biomarker” to describe HER2. A biomarker is any molecule in your body (here, in the breast cancer tissue removed during surgery) that can be measured and gives information about your health. In this case, HER2 status gives information about your breast cancer.
If your breast cancer is HER2-positive (see more below), estrogen receptor-positive (ER-positive) and progesterone receptor-positive (PR-positive), it may be called triple positive breast cancer.
If your breast cancer is HER2-negative (see more below), estrogen receptor-negative (ER-negative) and progesterone receptor-negative (PR-negative), it may be called triple negative breast cancer.
Testing for HER2 status
All breast cancers are tested for HER2 status. The main tests for HER2 status are:
- Immunohistochemistry (IHC), which detects the number of HER2 protein receptors on the cancer cells
- Fluorescence in situ hybridization (FISH), which detects the number of HER2 genes in the cancer cells
HER2 and early breast cancer
- HER2-positive breast cancer cells have a lot of HER2 protein. You may also hear the term HER2 over-expression.
- HER2-negative breast cancer cells have little or no HER2 protein.
About 10% to 20% of newly diagnosed breast cancers are HER2-positive [17,49].
HER2 status is part of breast cancer staging and helps guide your treatment.
Learn about HER2 status information on a pathology report.
HER2-positive early breast cancers and HER2-targeted therapies
HER2-positive breast cancers can be treated with HER2-targeted therapies, such as trastuzumab (Herceptin). These drug therapies target the HER2 receptor.
Trastuzumab and other HER2-targeted therapies are not used to treat HER2-negative early and locally advanced breast cancers.
Learn about HER2-targeted therapies in the treatment of early and locally advanced breast cancer.
Watch our video describing HER2 status and how it drives breast cancer growth.
HER2 and metastatic breast cancer
Immunohistochemistry (IHC) is a test which detects the amount of HER2 protein on the surface of the cancer cells. An IHC test can be scored as 0, 1+, 2+ or 3+.
HER2-positive metastatic breast cancers have high amounts of HER2 protein on the surface of the cancer cells. An IHC score of 3+ is considered HER2 positive. You may also hear the term HER2 over-expression.
HER2-low metastatic breast cancers have low, but detectable levels of HER2 expression. An IHC score of 1+ or 2+ shows a tumor is HER2-low.
HER2-ultralow metastatic breast cancers have very low levels of HER2 expression. HER2-ultralow cancers have an IHC score of 0, but the test detects a faint amount of HER2 on the cell membranes (surfaces) of a small percentage of the cancer cells (more than 0, but fewer than 10% of the cancer cells).
HER2-negative metastatic breast cancers have an IHC score of 0 with no HER2 detected.
HER2 status helps guide your treatment.
Learn about HER2 status and your pathology report.
HER2 status and HER2-targeted therapies for metastatic breast cancer
HER2-positive metastatic breast cancers can be treated with HER2-targeted therapies, such as trastuzumab (Herceptin). These drug therapies target the HER2 receptor.
Some HER2-low and HER2-ultralow metastatic breast cancers can be treated with the HER2-targeted therapy trastuzumab deruxtecan (Enhertu).
Learn more about treatment for HER2-positive metastatic breast cancers.
Learn more about treatment for HER2-low and HER2-ultralow metastatic breast cancers.
Proliferation rate
Proliferation rate is the percentage of cancer cells actively dividing.
In general, the higher the proliferation rate, the more aggressive the tumor tends to be and the more likely it is to spread to other parts of the body.
Tumors with a high proliferation rate (those that are growing fast) often have poorer survival than those with a low proliferation rate.
Proliferation rate could be a good predictor of survival and whether or not a tumor will respond to chemotherapy. However, there are issues related to the measurement of proliferation rate.
Proliferation rate isn’t routinely used by all health care providers to guide treatment.
Ki-67
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. Ki-67 is a proliferation antigen.
The result of this test is reported as the percentage of tumor cells with Ki-67 antigen. The higher the percentage, the more aggressive the tumor tends to be.
Learn about proliferation rate information (including Ki-67 test results) on a pathology report.
How does the information from a biopsy guide treatment?
Watch our video of Former Komen Chief Scientific Advisor Dr. George Sledge who talks about hormone receptor status and HER2 status and how both guide breast cancer treatment.
Learn about pathology reports.
Learn about factors that guide treatment for early and locally advanced breast cancer.
Learn about factors that guide treatment for metastatic breast cancer.
Find questions to ask your doctor when breast cancer is diagnosed.
Updated 03/06/25
This content is regularly reviewed by an expert panel including researchers, practicing clinicians and patient advocates.
