What is triple-negative breast cancer?


Triple-negative breast cancer is a term used to describe breast cancers that do not show expression of three common markers:

These three markers are important because they are often used to guide treatment. Breast cancers that are ER-positive, PR-positive, or HER2-positive can be treated with hormone therapy or targeted drugs. In triple-negative breast cancer, these options are not available because the tumour cells do not produce these proteins.

Why is this diagnosis important?

Calling a breast cancer “triple-negative” does not mean it is a specific type of cancer. Instead, it describes the results of the tests performed on the tumour. Many different kinds of invasive breast carcinoma can be triple-negative, including invasive ductal carcinoma of no special type (NST) and rarer forms such as metaplastic carcinoma.

Triple-negative breast cancers tend to:

  • Occur more often in younger women and in certain ethnic groups.

  • Grow and spread more quickly than some other types of breast cancer.

  • Have fewer treatment options compared to ER-positive or HER2-positive cancers.

How is triple-negative breast cancer diagnosed?

After a biopsy or surgery, a pathologist examines the tumour under the microscope. In addition, immunohistochemistry (IHC) is performed to test for ER, PR, and HER2.

  • If the tumour is negative for ER and PR (no significant staining is seen).

  • And if the tumour is negative for HER2 (no staining or only weak staining without gene amplification).

  • Then the tumour is classified as triple-negative.

What does this mean for treatment?

Because triple-negative breast cancers do not respond to hormone therapy (such as tamoxifen or aromatase inhibitors) or to HER2-targeted therapy (such as trastuzumab), the main treatments are surgery, chemotherapy, and radiation therapy. In some cases, newer options such as immunotherapy or targeted therapy based on genetic testing may be available.

Questions to ask your doctor

  • Is my breast cancer triple-negative?

  • What type of invasive breast carcinoma do I have (for example, NST, metaplastic, or another type)?

  • What stage is my cancer, and has it spread to lymph nodes or other organs?

  • What treatment options are recommended for me?

  • Are there clinical trials or newer therapies, such as immunotherapy, available for triple-negative breast cancer?

  • How will we monitor my response to treatment?

A+ A A-