Triple-negative Breast Cancer

What are breast cancer subtypes?

Breast cancer is complex, and not a one-size-fits-all disease. It can be broken down into different types based on an individual’s unique diagnosis. Subtype is one factor of a diagnosis that helps explain what may be causing the cancer to grow.

Currently, there are three main breast cancer subtypes:

  • Hormone receptor-positive (HR-positive) is the most common subtype, accounting for 72 percent of all breast cancers. With this diagnosis, the cancer cells contain receptors for the hormones estrogen and/or progesterone. This means the cancer depends on one or both of these hormones to grow.1
  • Human epidermal growth factor receptor 2-positive (HER2-positive) indicates the cancer cells have an excess of HER2 protein causing the cancer to grow. About 15 percent of breast cancers are HER2-positive.2
  • Triple-negative breast cancer (TNBC) is the absence of hormone receptors and excess HER2 protein, and accounts for about 15 percent of breast cancers.1,2
  • These are example subtypes. A person could also have a combination of subtypes, and/or other factors contributing to cancer growth.

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What is TNBC?

  • TNBC is unlike HR-positive and HER2-positive disease because it’s defined by what it lacks. People with TNBC do not have 1) estrogen receptors 2) progesterone receptors or 3) excess HER2 protein, which results in a triple-negative diagnosis. This makes TNBC particularly difficult to treat because targeted therapies for HR- and HER2-positive disease do not work in TNBC.1,2
  • TNBC is more likely to be diagnosed at a later stage with, on average, a larger tumor size and cancer cells that look more abnormal under a microscope compared to other subtypes.

Who is affected by TNBC?

  • An estimated 268,670 new cases of breast cancer are expected to be diagnosed in the U.S. in 2018.3
    • TNBC accounts for about 40,300 of these cases.4
  • TNBC tends to be more common in younger women and in women who are African-American or Hispanic/Latina.1
    • In the U.S., TNBC is twice as likely to occur in African American women compared to Caucasian women, and is twice as deadly.5
    • Women diagnosed with breast cancer before age 40 are 53 percent more likely to have TNBC compared to women in their sixties.5

How is TNBC treated?

  • Over the past 20 years, few advances have been made in treating TNBC. Current treatment options include chemotherapy and radiation.1
  • Today scientists are making inroads in understanding its biology, in hopes of identifying new ways of treating this disease.

To learn more about our work in breast cancer, check out our Breast Cancer hub.

1 American Cancer Society. Breast Cancer Hormone Receptor Status. Accessed October 2, 2018.
2 American Cancer Society. Breast Cancer HER2 Status. Accessed October 2, 2018.
3 American Cancer Society. Cancer Facts & Figures 2018.
4 Kohler BA, et al. Annual Report to the Nation on the Status of Cancer, 1975-2011, Featuring Incidence of Breast Cancer Subtypes by Race/Ethnicity, Poverty, and State. Journal of National Cancer Institute 2015 Mar 30;107(6):djv048.
5 Bauer KR, et al. Descriptive Analysis of Estrogen Receptor (ER)-Negative, Progesterone Receptor (PR)-Negative, and HER2-Negative Invasive Breast Cancer, the So-called Triple-Negative Phenotype. Cancer 2007 March ;10.1002/cncr.22618