Cancer Types

Breast Cancer

Information about breast cancer.

What is breast cancer?

Breast cancer is when abnormal cells in the breast begin to grow and eventually form a growth (tumour) which can spread within the breast or around the body. Breast cancer can develop over several years.

Who can be affected by breast cancer?

Breast cancer is more common in people over the age of 50 years, although a quarter of cases occur in younger people. The chances of getting breast cancer increase with age.

Men and trans-women, intersex and non-binary people can also get breast cancer. Breast cancer in men is very uncommon but it’s still very important a lump or other breast symptom is checked out by a doctor.

Māori women experience higher rates of breast cancer, and Māori and Pasifika women more commonly get breast cancer at a younger age.

Risk factors

Anything that can increase your risk is called a risk factor. Having one or more of these risk factors does not necessarily mean that you will develop breast cancer.

Some of these risk factors can't be changed (e.g. age) while others can (e.g. physical activity).

Personal risk factors:
  • Increasing age
  • Dense breast tissue (this is genetic)
  • Drinking alcohol
  • Overweight or obesity
  • Physical inactivity
Family history and genetic risk factors:
  • You have had cancer before
  • You have had DCIS (Ductal carcinoma in situ) or LCIS (Lobular carcinoma in situ) before
  • Your mother, sister, aunt or grandmother has had breast cancer and/or ovarian cancer (this may be due to a rare gene in the family)
Reproductive risk factors:
  • Starting menstrual periods younger than 12 years
  • Higher levels of the naturally-occurring hormone oestrogen
  • Being older when your first child was born (30 years+)
  • Not breastfeeding
  • Not having given birth to any children
  • Later age at menopause (55 years or older)
Medications and treatments that can contribute to breast cancer:
  • Combined menopausal hormone therapy/HRT
  • Combined oral contraceptive pill
  • Radiation therapy
  • Exposure to diethylstilbestrol (DES; a drug that was prescribed to pregnant women up until the 1960s to reduce the risk of miscarriage) while pregnant

Signs and symptoms

There may be no warning signs that you have breast cancer. Some signs and symptoms may include:

  • A new lump in the breast
  • Nipple discharge
  • Changes in the nipple, such as turning inwards, ulcers, persisting redness
  • Changes in the breast such as shape or size or changes on the skin of the breast such as skin dimpling, redness
  • Pain in the breast that doesn't go away

Although these symptoms can be caused by conditions other than cancer, it's important to get them checked by your doctor as soon as possible.

Finding breast cancer early

It's important that women of any age take the time to learn the normal look and feel of their breasts. Knowing what's normal will help to find any breast changes. Changes to look out for include any of the signs and symptoms above. Most of the time, any changes to your breasts will not be cancer but if you find anything unusual, see your doctor to be sure.

Breast screening mammography

You are more likely to survive breast cancer if it is found early, and it is still small. Mammograms can detect breast cancer and show changes inside a breast before they can be felt.

You can have a free mammogram every two years if you're an eligible female aged 45 to 69 years. Go to Having a Mammogram to find out if you're eligible and what's involved.

Testing and diagnosis

If a mammogram picks up something unusual, more tests might need to be done.

It may involve your radiologist (a doctor who specialises in reading mammograms) taking a closer look at what was found. You may also need a biopsy, which is a procedure to remove a small amount of tissue or cells from your breast so they can be looked at under a microscope.


If you have breast cancer, you will have a team of health professionals looking after your care.

You may be offered:

  • A lumpectomy (surgery to remove only the cancer)
  • A mastectomy (surgery to remove the breast)
  • Radiation therapy (x-rays to destroy the cancer cells)
  • Hormone treatment (medicine for women with hormone receptors on their breast cancer cells)
  • A combination of surgery, radiation therapy and hormone treatment
  • Targeted therapy (drugs to stop the growth and spread of cancer)

The treatment for breast cancer depends on many things, including the type and stage (how far it has spread), your age, general health and preferences.

After your treatment

If you have had breast cancer, it is recommended that you have regular check-ups with your doctor. This is because there is a higher risk of developing breast cancer again. Any side effects of treatment or medications can also be monitored. The timing of these check-ups is based on your circumstances. Women who have had a mastectomy can still have a mammogram of the other breast.

If you notice any breast cancer signs or symptoms see your doctor as soon as possible. Do not wait until your next scheduled appointment.

Helpful websites

Breast Cancer Foundation

Breast Cancer Aotearoa Coalition

Breast Screening information