Mammogram

A mammogram is a low-dose X-ray of your breast tissue and can be done in 2D or 3D. It's used to find small cancers at an early stage, before anything can be seen or felt, and when there's a good chance of successful treatment.

Mammograms are also known as breast screening. In Aotearoa New Zealand breast screening mammograms are free for women from 45 to 69 years of age. 

Video: What is a mammogram?

There are 2 main types of mammogram, 2D mammography and 3D mammography (also known as digital breast tomosynthesis). A standard 2D mammogram is made up of 4 images (2 of each breast) taken in 2 views. A 3D mammogram is performed in the same way as a standard 2D mammogram, but the mammogram machine moves in an arc to take images of your breast from different angles. This allows your breast tissue to be seen in more detail. A 3D mammogram can be between 4 to 8 images depending on the equipment used.

Watch a video about the difference between 2D and 3D (tomosynthesis) mammograms(external link). 

Note: Not all breast screening services or providers will offer 3D (tomosynthesis) mammograms in Aotearoa New Zealand, and there may be a cost involved.

A mammogram, either 2D or 3D, is the recommended test for breast cancer screening for women 40 years of age and older. Mammograms can show changes and abnormalities in your breasts at an early stage, before anything can be seen or felt, when there's a very good chance of successful treatment.

Mammograms can detect about 75% of unsuspected cancers in women under 50 years of age and 85% in women over 50. 

If you have a concern about your breasts you may be asked to have a mammogram as part of the assessment process. 

The Breast Cancer Foundation New Zealand recommends you consider having regular screening mammograms from 40 years of age. In Aotearoa New Zealand, you're able to have a free mammogram every 2 years if you're 45 to 69 years of age. You can book this through BreastScreen Aotearoa(external link) (freephone 0800 270 200). This programme isn't available to you if you don't qualify for publicly funded healthcare in Aotearoa New Zealand and if you don't live in New Zealand. Talk to your healthcare provider about options for breast screening.

What if I am under 45?

If you are between the ages of 40 and 45, you may choose to start screening earlier. This isn't publicly funded, so you'll have to pay for this yourself. Many private providers allow you to self-refer for a screening mammogram from the age of 40. Routine mammograms are not recommended for women under 40 unless you're considered high risk.

If you're under the age of 45 and have a high risk of developing breast cancer, you may be able to start regular funded screening with mammography earlier. High-risk factors are:

• You've previously had breast cancer.
• Your mother or sister developed breast cancer before menopause or had breast cancer in both breasts.
• You've had a breast biopsy and the results indicated you have an ‘at-risk lesion’ for developing breast cancer.
• You or a close family member has a known genetic abnormality that increases your breast cancer risk.

If any of these apply to you, or you think you may be at high-risk, talk to your healthcare provider to see what services are available to you.

Like most tests, mammograms are not perfect, and have their limitations.

• A mammogram can show an abnormality which after further testing turns out not to be a cancer. This is called a false positive result.
• Some cancers don't show up or are not easily seen on a mammogram. This is more likely to happen in women with dense breast tissue, as the breast density can make it harder to read a mammogram and the density can ‘mask’ a cancer. This is called a false negative result. Watch a video about breast density and why it's important(external link). 
• The radiologists looking at the mammogram may miss the cancer. This can happen, no matter how experienced the radiologist and team are. This is called a false negative result.
• Some breast cancers are fast growing and can develop between regular mammograms. 

For these reasons, it's important to be breast aware, to know your breasts and look at them regularly to identify any changes. Despite its limitations, mammography is still the proven way of finding breast cancers early enough to reduce your risk of dying of breast cancer, particularly for women over the age of 50.

Read more about breast lumps and changes.

You'll need to undress from the waist up, so you may want to wear clothing that's easy to remove, such as a separate top and bottom. You'll be provided with a gown when you have your mammogram and your privacy will be protected as much as possible.

Don't use talcum powder, creams, or deodorants on the day of your mammogram as these can show up on the mammogram.

You may wish to bring:

• previous mammograms results if you’ve had imaging overseas
• your glasses if you need them for reading as you'll need to fill in a form
• a support person or member of your whānau.

During the procedure, your breasts will be positioned in the mammogram machine 1 at a time, and compression will slowly be applied to your breast to hold it in place while the picture is taken. While this may be uncomfortable, compression is an important part of the mammogram as it helps to spread the tissue out so it can be seen better. It will only take a few seconds for each picture to be taken. The mammographer will want you to be as comfortable as possible, so please discuss any concerns you have with them.

Video: Mammogram screening – your first mammogram and what to expect

Video: Watch Stacey have her mammogram

(Breast Cancer Foundation, NZ, 2020)

The whole visit, including waiting and imaging time, is usually about 30 minutes.

The results of the mammogram will be sent directly to you, and to your healthcare provider if you've agreed to this. If an area of interest is picked up on your mammogram that requires further investigation, you'll be contacted and asked to return for further imaging. 

• Only a very small amount of radiation is used in mammography, so the radiation risk is extremely low.
• Like many tests, there's a small false negative rate. This means some breast cancers will be missed on mammography. If you have dense breast tissue, you have a higher risk of breast cancer being missed on mammogram. It may be recommended you undertake additional screening by having a breast ultrasound or breast MRI in addition to mammography.
• There's also the risk of a false positive, which means that not all abnormalities detected on mammography turn out to be breast cancer upon further testing. Having regular mammograms reduces the false positive rate, as the radiologist reading your mammogram will have more previous imaging to compare your current mammogram with, to be able to identify any changes over a period of time.