What is triple-negative breast cancer?

Triple-negative breast cancer does not have estrogen or progesterone receptors. It does not produce much or any HER2 protein. Because treatments that target these receptors and HER2 will not work, triple-negative breast cancer can be more challenging to treat. However, treatments such as chemotherapy, immunotherapy, and surgery are available for people with triple-negative breast cancer. Your doctors will recommend treatment based on factors including the stage of the cancer and your overall health.

Triple-negative breast cancer is a subtype of breast cancer. The name refers to three elements that can influence breast cancer growth:

• estrogen, a hormone
• progesterone, a hormone
• human epidermal growth factor receptor 2 (HER2), a protein

Triple-negative breast cancer lacks receptors for estrogen and progesterone. These receptors are proteins on the surface of cells that influence cell growth. The cancer cells also do not produce excessive amounts of HER2.

Therefore, the condition is negative for, or lacks, all three of these elements. As a result, hormone therapy and HER2-targeted therapies will not work.

However, according to the Centers for Disease Control and Prevention (CDC), triple-negative breast cancer usually responds well to chemotherapy.

What causes triple-negative breast cancer?

Like other types of cancer, experts do not fully understand what causes triple-negative breast cancer.

Cancer begins when healthy cells begin to grow out of control. This happens when genes inside the cell change, or mutate, because of an error during cell division or from damage to DNA.

It is not entirely clear how, when, or why the mutations occur. It is likely a combination of genetic and environmental factors. This means that some people may be at higher risk of cancer than others. However, it is possible to develop cancer without any obvious risks.

Learn more about the BRCA1 genetic mutation and triple-negative breast cancer.

What are the signs and symptoms of triple-negative breast cancer?

There are no signs or symptoms specific to triple-negative breast cancer. This means they will be the same as other forms of breast cancer. One of the most common signs is a lump or mass in the breast, often discovered accidentally.

Other signs and symptoms may include:

• changes in the size, shape, or appearance of the breast or nipple
• newly inverted or retracted nipple
• nipple soreness, tenderness, or discharge other than milk
• skin changes on the breast or nipple
• swelling or fullness in part or all of the breasts
• swelling in the lymph nodes of the armpit

Contact your doctor right away if you have any of these symptoms. Regardless of the cause, an early diagnosis often leads to a better outcome.

How do doctors diagnose triple-negative breast cancer?

To diagnose breast cancer, your doctors will perform:

• a clinical examination, which includes asking about your medical history and performing a physical examination
• imaging tests, such as mammograms or MRI scans
• a tissue biopsy, taking a small tissue sample for further analysis

If your doctors confirm the presence of cancer cells, they will then stage the disease. This means they will determine how large the tumor is and if it has spread beyond the original site.

Learn more about staging and progression of triple-negative breast cancer.