Breast cancer is one of the most commonly diagnosed cancers in the world. There are many different types and subtypes of breast cancer that are defined by where in the breast they begin, how much they have grown or spread and how they behave. One of the more aggressive types is triple-negative breast cancer (TNBC).

What’s triple-negative breast cancer?

The tumours of patients with breast cancer may be tested for three receptors, or proteins, that make cancer grow. If the tumour tests negative for estrogen and progesterone receptors and does not over express HER2, then that patient is diagnosed with TNBC.

In New Zealand, around 3,500 people are diagnosed with breast cancer each year. About 10-20% of breast cancers are TNBC.

Risk factors for triple-negative breast cancer

Primary risk factors for TNBC include:

• Sex: People assigned female at birth are at higher risk for TNBC compared to people assigned male at birth.
• Age: TNBC is more common in women younger than other breast cancer types.
• Genetic mutations: Mutations in genes such as BRCA1 and BRCA2 are strongly associated with TNBC.

What are the symptoms of breast cancer?

TNBC can have the same signs and symptoms as other common types of breast cancer. However,  signs and symptoms of breast cancer differ from person to person, and some will never show symptoms.

Here are some symptoms of breast cancer to watch out for:

Many breast changes are not a sign of cancer, but it’s always important to have any changes checked by a doctor.

The Breast Cancer Foundation NZ recommends women start being breast aware from the age of 20.

This means understanding the usual look and feel of your breasts and checking for any changes.

How is triple-negative breast cancer diagnosed?

If you’re experiencing symptoms, speak with your doctor, especially if you have a higher risk of having TNBC. Some tests include:

• A breast exam by a doctor: During a breast exam, your doctor will check your breasts for any possible signs of breast cancer or other breast problems.
• Mammogram: An X-ray of the breast that allows doctors to look for changes in breast tissue. Mammograms can often find breast cancer early.
• Magnetic resonance imaging (MRI): An MRI uses radio waves and strong magnets to make detailed pictures of the inside of the breast. Doctors use MRIs along with mammograms to screen people who are considered at high risk for breast cancer.
• Ultrasound: An ultrasound uses sound waves and their echoes to make computer pictures of the inside of the breast. While not typically used as a routine screening test for breast cancer, an ultrasound can be useful for looking at some breast changes such as lumps – especially when they can be felt but not seen on a mammogram.
• Biopsy: After a breast cancer diagnosis is made with a biopsy, a health care provider may determine whether a patient has TNBC with an assessment of cells from that biopsy, which are checked for estrogen, progesterone and HER2 receptors, to determine the cancer subtype.

For further information about breast cancer or if you notice any breast changes, please talk to your doctor.

If you require extra support if you’ve been diagnosed with breast cancer, it may be helpful to reach out to a patient organisation.

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^{NZ-NON-00454 V1.0 Last Updated November 2024}