A mammogram is essentially a low dose x-ray which gives a photograph of the breast that doctors can use to identify any abnormalities.

Mammograms are used as:

  • a screening tool for healthy women to check for any developing problems in the breast
  • a diagnostic tool to get more information about a specific area of concern.

A mammogram is currently the standard way to detect early breast cancer. If breast cancer is detected early, treatment can begin early and a woman has a greater chance of survival. 

Mammograms have been shown to lower the risk of dying from breast cancer by 20 to 30 per cent in women over the age of 50 (World Health Organisation). A new Swedish study has found that mammograms can reduce the risk of dying from breast cancer by 29 per cent in women aged 40 to 49 ((Cancer 29/09/10). Mammograms literally save lives.

What happens during a Mammogram

During a mammogram you will place your breast between the two plates of an x-ray machine (pictured right). The breast is then flattened between these plates while the x-ray is taken. Sometimes, this can feel uncomfortable and for some it might feel slightly painful, but it only lasts a few seconds while the x-ray is taken.

The mammogram x-ray identifies lumps or changes in the breast tissue which may develop into breast cancer over time. A mammogram is a very good way of identifying lumps or changes in the breast which cannot be felt by a woman or her doctor.

Going for a mammogram may be a scary experience, especially as you wait for results or if an abnormality is found. 

You will usually receive the results of your mammogram within two weeks. If you have had a previous mammogram then your past x-rays will be compared with your latest picture to pick up any changes.

A small number of women will be asked to return for a further check up because something of concern has been found.  This could involve a further mammogram, an ultrasound or perhaps a biopsy.  If you are asked to return for further tests, remember that many breast lumps found (up to 9 out of 10) are harmless or benign. For more information see our pages on biopsies and other diagnostic tests. 

Accuracy of mammograms

A mammogram will frequently pick up breast changes, but it is not a 100 per cent accurate. Sometimes a mammogram will suggest a problem is present, when in fact everything is alright.

And sometimes a mammogram will miss developing breast cancer. This is usually because:

  • some cancers do not show up on a mammogram especially in younger women with more dense breast tissue

  • the radiologist does not identify the cancer

  • a rapidly growing cancer may be missed between two-yearly mammogram appointments.

Some clinics in New Zealand use digital mammography in which a digital image is taken of the breast, rather than the more common x-ray film mammography.   Studies have shown that digital images can result in a more accurate identification of breast cancer in some women.  This is because digital images can be manipulated so that images can be examined more closely which is particularly useful when examining mammograms of women with dense breasts.   

 Those who may benefit from a digital mammogram are: 

  • women aged under 50

  • women with very dense or extremely dense breasts

  • pre or peri-menopausal women (women who had a menstrual period with the last 12 months)

Despite the fact that neither digital nor film mammograms are 100 per cent accurate, they are still the most commonly used way to pick up breast cancer early enough to reduce your risk of dying from the disease.

If you are concerned about a lump which may have developed between your two-yearly mammograms, you should consult your doctor immediately.

The BreastScreen Aotearoa programme

BCAC encourages all women aged between 45 and 69 participate in the BreastScreen Aotearoa free screening programme. Under this programme, you are entitled to a free mammogram every two years. Find out more about this programme here.

If you are younger than 45 or older than 69 you can ask your doctor to refer you to a private radiologist. You will have to pay for your mammogram, but if you have medical insurance this may be reimbursed.