Mammograms are breast x-rays. When you have a mammogram, the medical radiation technologist (radiographer) who takes the x-rays places each breast in turn between two plates on the x-ray machine. The plates hold the breast firmly for a few seconds while the x-rays are taken. Many women find this uncomfortable, and a few find it painful. It does not harm the breasts.

Mammography screening:

• detects cancer but cannot prevent it
• does not give a guarantee that cancer is not present
• reduces the risk of dying from breast cancer but does not eliminate it.

The mammogram is looking for breast lumps and changes in breast tissue that may develop into problems over time. They can find small lumps or changes that a health care practitioner or woman cannot feel when doing a physical breast examination.  Breast lumps or growths can be benign (not cancer) or malignant (cancer). 

Finding breast cancer early means a woman has a better chance of surviving the disease.  There are also more choices for treatment when breast cancer is found early.  It also increases the likelihood that surgical options that conserve the breast can be offered.

Mammography screening reduces a woman's risk of dying from breast cancer.  One of the reasons it cannot stop every woman with breast cancer from dying is that the cancer may already have been in the body for up to ten years or longer by the time the mammogram detects it.  Even when small, a few breast cancers may already have spread to other parts of the body.

How accurate are mammograms?

Like other screening tests, mammograms are not perfect. A mammogram may suggest that something is not right when, in fact, all is well. This is called a false positive result.

You may notice symptoms of breast cancer between your two-yearly screening tests. This is called an interval cancer and can happen because:

• some cancers do not show up on a mammogram. This is more likely in women before menopause who often have dense breast tissue. The density usually reduces as women age and go through menopause
• the radiologist (x-ray doctor) looking at the mammogram may miss the cancer. This will happen sometimes, no matter how experienced the radiologist
• sometimes a fast-growing cancer will develop.

Despite this, mammograms are the only proven way for finding breast cancers early enough to reduce your risk of dying from breast cancer.