Breast density

Breast density overview

Breast density has emerged as a highly discussed topic, generating much interest here in Australia and overseas.

BreastScreen Victoria is part of the BreastScreen Australia program, which regularly reviews evidence to inform future program changes at a national level.

At BreastScreen Victoria, we understand the risks associated with breast density and its impact on breast cancer screening.  

We have developed answers to commonly asked questions about breast density to better inform you about its relevance to breast health.

We continue to recommend women between the ages of 50 to 74 have a breast screen (mammogram) every 2 years as it is still considered the most effective way to detect breast cancer early.

Breast density - frequently asked questions

A breast screen is a low-dose x-ray of the breast. It is also called a mammogram. Breast screens can find cancers that are too small to see or feel.  

The earlier breast cancer is found, the better the chance of a positive health outcome. 

Visit our website to find out more about breast cancer screening methods.  

Cancer is the name for a group of diseases that develop when the body’s cells grow in an uncontrolled way and spread into the body’s tissues. Breast cancer is cancer that starts in the breast tissue and there are several different types of breast cancer.

Breasts are made up of a combination of tissue; fatty, glandular (the milk ducts and lobules) and connective tissue (which helps hold everything in place).   

Women with high breast density have more fibroglandular tissue and less fatty tissue.

There is much variation in breast density. Approximately 50% of women aged 40 to 74 years have dense breasts, and about 10% of women are classified as having extremely dense breasts.   

Breast density usually reduces with age as most women's breasts change through menopause becoming more fatty and less dense.  

A very small number of women maintain high breast density after menopause. Post-menopausal women who take hormone replacement therapy (HRT) typically have increased breast density.

Breast density can only be measured from a breast screen. Usually this is done by one of the following options: 

  • A radiologist analyses the breast screen to make a subjective estimate of density.  
  • A computer program can provide a volumetric measurement. 

Clinical assessment of breast density is commonly classified into four categories using the Breast Imaging Reporting and Data System (BI-RADS).  

BI-RADS categories include: 

A: Breasts are almost entirely fatty (approx. 10% of women) 

B: Breasts have scattered areas of dense tissue (approx. 40% of women) 

C: Breasts have high areas of dense tissue. The mix of non-dense and dense tissue may hide small cancers (approx. 40% of women) 

D: Breasts are extremely dense, reducing the visibility of cancers on a breast screen (approx. 10% of women) 

Women in the C or D category are regarded as having high breast density.

x-ray images of breast tissue showing different categories of breast density

Breast imaging reporting and data systems (5th edition). Note higher amount of dense tissue (white areas) in C and D

On a breast screen, fatty breast tissue appears black/grey in colour and the glandular and connective tissue appear white in colour.  

The greater the amount of glandular and connective tissue relative to fat in the breast, the whiter the breast screen appears.  

In breast screens, high breast density with large amounts of white may camouflage a cancer.

Increased breast density is associated with an increased risk of breast cancer.  The risk is also influenced by a range of other factors including age, family history of breast and/or ovarian cancer, alcohol intake, smoking, weight, diet and other lifestyle and environmental factors.  

Age is the biggest risk factor for developing breast cancer, with most breast cancers occurring in women over 50. Importantly, most women who develop breast cancer have no known risk factors other than being a woman and getting older.

Even with dense breasts, a breast screen every two years is the still the best way to detect breast cancer early in women between the ages of 50 and 74 with no breast symptoms.

There are extra screening tests available and should be considered in discussion with a doctor. These may include ultrasound, contrast enhanced mammography, magnetic resonance imaging (MRI) and 3D breast screen (digital mammography tomosynthesis).  

Medicare doesn't cover these additional tests. Medicare rebates for private breast screenings are only available to women with symptoms or a family history of breast cancer.

BreastScreen Victoria does not currently measure or report breast density on your breast screen results. 

Women who wish to be informed about their breast density, should see their doctor for a referral to a private radiology provider who offers breast density measurement. This breast screen is not covered by Medicare. The Medicare rebate for private breast screens is only available for women with symptoms or a family history.  
Don't be afraid to ask your doctor about your breast cancer risks.

BreastScreen Victoria does not currently measure or report breast density on breast screen results. We acknowledge that breast density is an important issue, and it may affect the frequency and method of screening in the future.  

BreastScreen Victoria is part of the BreastScreen Australia program, which regularly reviews evidence to inform future program changes at a national level.