FAQs

Breast density is typically measured from a mammogram (an x-ray of the breast). It is also referred to as mammographic density. Dense breasts have more glands and fibrous tissue, compared with breasts that aren't dense. These dense regions show up white and bright on the mammogram. Non-dense breasts have more fatty tissue which appears dark on the mammogram.

Having dense breasts means that a woman is at greater risk of developing breast cancer in the future, and there is a chance that the density could hide a cancer on a mammogram.

Breast density is often described using these 4 categories:

Category A Mostly fatty: The breasts are made up of mostly fat and contain little fibrous and glandular tissue. This means the mammogram would likely show anything abnormal.

Category B Scattered density: The breasts have quite a bit of fat, but there are a few areas of fibrous and glandular tissue.

Category C Heterogeneously dense: The breasts have many areas of fibrous and glandular tissue that are evenly distributed through the breasts. This can make it hard to see small masses in the breast.

Category D Extremely dense: The breasts have a lot of fibrous and glandular tissue. This may make it hard to see a cancer on a mammogram because the cancer can blend in with the normal tissue.

Pictured below are mammograms showing breasts from each of these categories.

At first, finding out you have extremely dense breasts might be confronting. However, knowing this information will help you be part of decision-making around how to manage your breast cancer screening and your breast cancer risk. It is estimated that around 10% of women have extremely dense breasts.

Managing your breast cancer screening:

Mammography is the recommended tool for breast cancer screening regardless of breast density. Although breast density can hide cancer, many cancers can still be detected by mammography in women with extremely dense breasts.

There are also supplementary screening options such as MRI, contrast enhanced mammography and ultrasound that can sometimes detect breast cancers in dense breasts that are not detected by mammography. These supplementary screening options are not currently recommended in Australian guidelines, however MRI has been recommended by the European Society for Breast Imaging as an effective screening tool for women with extremely dense breasts. The Royal Australian and New Zealand College of Radiologists describe use of MRI as aspirational, since there are economic, human resources and accessibility issues preventing MRI as a feasible breast cancer screening tool in Australia.

We encourage women to discuss their options for managing extremely dense breasts with their General Practitioner (GP) or health professional, and make informed decisions about the most suitable course for their individual circumstance. When deciding whether or not to pursue supplementary screening, women can consider that these options also come with out-of-pocket expenses and a risk of a false positive result (a result that indicates that breast cancer may be present when it is not). A false positive can be a distressing experience, with additional tests sometimes being required such as a breast biopsy.

Managing your breast cancer risk:

Although breast density is a risk factor for breast cancer, most women with extremely dense breasts will not develop cancer. We encourage women to learn more about their individual breast cancer risk, what risk factors they have and how these can be managed. This free online breast cancer risk calculator can help you understand your chance of developing breast cancer. Further information about breast cancer risk factors is available from Cancer Australia.

Being “breast aware” is important for all women, but particularly women with extremely dense breasts. Breast density cannot be determined by touch but it is still important to get to know how your breasts feel and check them regularly. Any changes should be reported to your GP or health professional. Regular breast examinations can also be scheduled with your GP.

If you attended BreastScreen Western Australia for breast cancer screening, you may receive a letter saying you have dense breasts. “Dense breasts” is a general term for breast density Categories C (heterogeneously dense) or D (extremely dense). It is estimated that around 35% of women have heterogeneously dense breasts and around 10% of women have extremely dense breasts.

Being “breast aware” is important for all women, but particularly women with dense breasts. Breast density cannot be determined by touch but it is still important to get to know how your breasts feel and check them regularly. Any changes should be reported to your General Practitioner (GP). Regular breast examinations can also be scheduled with your GP.

Although breast density is a risk factor for breast cancer, most women with dense breasts will not develop cancer. We encourage women to learn more about their individual breast cancer risk, what risk factors they have and how these can be managed. This free online breast cancer risk calculator can help you understand your chance of developing breast cancer. Further information about breast cancer risk factors is available from Cancer Australia.

Breast density is a risk factor for breast cancer, however most women with dense breasts do not develop cancer. Women with Category C heterogeneously dense breasts have a 1.6-fold increased risk compared to women with Category B scattered density. Women with Category D extremely dense breasts have a 2.1-fold increased risk compared to women with Category B scattered density. There are many other factors that affect breast cancer risk and it is important to consider all these factors, not just breast density alone. This breast cancer risk calculator can help you understand your chance of developing breast cancer.

Both breast cancer and dense breast tissue appear white on a mammogram so the dense breast tissue can hide the cancer, making early detection more difficult.

The mammograms below show a mostly fatty breast and an extremely dense breast. The arrow is pointing to a cancer which you can see in the mostly fatty breast. It is more difficult to detect a cancer in an extremely dense breast, as it can be hidden in the dense tissue.

Around 10% of women aged between 40-74 years have extremely dense breasts, and 35% have heterogeneously dense breasts. Breast density decreases with age, so dense breast tissue is more common in younger women compared to older women.

The graph below shows the proportion of women from the different breast density categories across different age groups. This graph is based on American data, but recent studies suggest the proportions would be similar for Australian women.

Research suggests that breast density gradually reduces as we age. Having children, breastfeeding, and going through menopause reduces breast density naturally.

Tamoxifen is a medication that has been shown in research to reduce breast density, although it works in some women better than in others.

At first, finding out you have high breast density might be confronting. However, knowing this information will help you be part of decision-making around how to manage your breast cancer screening and your breast cancer risk.

Being “breast aware” is important for all women, but particularly women with higher breast density. Get to know how your breasts feel and check them regularly. Any changes should be reported to your General Practitioner (GP). Regular breast examinations can also be scheduled with your GP.

There are supplementary screening options such as ultrasound and MRI, however use of these options comes with a high rate of false positives (a result that indicates that breast cancer is present when it is not). A false positive can be a distressing experience, with additional tests sometimes being required such as a breast biopsy.

We encourage women to discuss their breast cancer risk with their GP or health professional, and make informed decisions about how to manage their individual risk.

You cannot see, touch, or feel how dense your breasts are; a mammogram is needed to determine your breast density.

During puberty, the glands, fibrous tissue and fatty tissue that determine density form in the breast. However, a mammogram is required to measure density and this is not recommended until a women is older, usually aged 40 or over.

No. Breast size does not relate to how dense your breast is on a mammogram. Dense breasts are related to how much fat your breast has compared to fibrous and glandular tissue, and this can only be measured by a mammogram.

No. How breasts look or feel is not related to how dense your breast is on a mammogram. Dense breasts are related to how much fat your breast has compared to fibrous and glandular tissue, and this can only be measured by a mammogram.

The association between weight loss and breast density is complicated. Losing weight can lead to having less fatty tissue in your breasts so the percentage of dense tissue in the breast can become a little higher. However, weight loss may also help reduce the amount of dense tissue in the breast. Larger studies need to be conducted to better understand changes in breast tissue composition and their association with breast cancer risk.

All tests require a mammogram in order to measure breast density. The most accurate tools for measuring breast density, such as Volpara and Qantra, use specific software integrated into the digital mammogram equipment. Radiologists can also visually assess a mammogram and assign a breast density category according to the BI-RADS scale. This visual assessment doesn’t require specialised software and is less accurate, as radiologists sometimes disagree on the breast density category.

Hormone replacement therapy (HRT) can increase breast density and increase the risk of breast cancer. The benefits of taking HRT for menopause symptoms need to be weighed against the increased risk of breast cancer. Generally it is recommended that women take HRT for the minimum amount of time needed to control their menopause symptoms.

Approximately 1% of all breast cancers occur in males. We do not know if breast density is a risk factor for men because the incidence is so rare and men do not usually attend breast cancer screening programs.