Breast Density frequently asked questions

There has been discussion in the media about the issue of breast density and how it may relate to mammographic screening. BreastScreen NSW acknowledges that this may cause concern among women who may be confused about what this means for them and what action they should take. The below information will assist with these concerns.

What is breast density?

Breasts are made up partly of fat and partly of fibroglandular tissue. While fat appears dark on a screening mammogram, fibroglandular tissue appears ‘dense’ or white.[i]

Each woman’s breasts are different and contain a unique mix of fatty and dense tissue. For reasons that are not fully understood, some women will have lots of dense breast tissue, while others will have little.[ii]

A woman with lower breast density will have more fatty tissue, whereas a woman with higher breast density will have less fatty tissue.[i] Dense breast tissue is common and normal, occurring in around one third of women aged over 50.[ii] It usually reduces with age. The images below show normal breasts with different densities.

How is breast density measured?

Breast density cannot be seen or felt. Breast density can either be measured by a radiologist analysing a woman’s mammogram and providing a density score, or by using computer software to identify and score the amount of breast density present on a woman’s mammogram.

There is no consensus about the most effective way to measure or manage breast density.[iv] Measuring breast density can also be problematic, as a woman may get different results depending on how her image is analysed.[v] If these variations are reported, it is likely to cause confusion and unnecessary anxiety to women.[iii],[vi]

How common are dense breasts?

There are no statistics on the number of women in Australia with dense breasts because this information is not currently recorded, however international research suggests[vii]:

  • more than half of women under the age of 50 have dense breasts
  • about 40 percent of women in their 50s have dense breasts
  • about 25 percent of women age 60 and older have dense breasts.

Breasts tend to become less dense as women get older, especially after menopause, as the glandular tissue degenerates and the breasts become more fatty. A range of other factors also contribute to breast density such as hormones, Body Mass Index and genetics.[viii]

Does breast density affect the accuracy of mammography?

Mammography is still the best breast cancer screening test for women aged 50-74, even with dense breast tissue.[ix]

Detecting breast cancer using mammograms can be more difficult in women with dense breasts. This is because dense breast tissue appears white on a mammogram, and so too does breast cancer. This means the cancer can be ‘masked’ by dense breast tissue, making it harder to see.[i],[x]

As breast density increases, the ability of mammography to show cancers generally decreases. As a result, women may be given an ‘all clear’ where cancer is present, or women may be recalled for further testing when there is no cancer present.[x]

Does breast density increase the risk of breast cancer?

Research shows that increased breast density is associated with an increased risk of breast cancer.[xi],[xii] The risk of developing breast cancer is also influenced by a range of other factors such as growing older, having a strong family history, being overweight, drinking alcohol and other lifestyle and environmental impacts.[xiii]

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

It is important for all women to be breast aware and to know the normal look and feel of their breasts. Interval cancers, which can develop in between screening appointments, can occur in all women, including those with dense breasts, so breast awareness is important. If women are concerned about their breast cancer risk or notice any changes in their breasts they should see their GP.

Should women with dense breasts have screening mammograms?

Yes. Mammography is still the best breast cancer screening test for asymptomatic women aged 50-74, including women with dense breast tissue. Mammography is also the only screening tool that has been demonstrated to lower breast cancer mortality.[ix] The BreastScreen Australia program has been found to reduce breast cancer mortality by around 21-28% for women 50-69 years of age.[xiv]

While the accuracy of mammography can be lower in women with dense breasts, it is still the best test for population-based screening.

It is important for all women to be breast aware and to know the normal look and feel of their breasts. If women are concerned about their breast cancer risk or notice any changes in their breasts they should see their GP.

Should women with dense breasts have screening mammograms?

Yes. Mammography is still the best breast cancer screening test for asymptomatic women aged 50-74, including women with dense breast tissue. Mammography is also the only screening tool that has been demonstrated to lower breast cancer mortality.[ix] The BreastScreen Australia program has been found to reduce breast cancer mortality by around 21-28% for women 50-69 years of age.[xv]

While the accuracy of mammography can be lower in women with dense breasts, it is still the best test for population-based screening.

It is important for all women to be breast aware and to know the normal look and feel of their breasts. If women are concerned about their breast cancer risk or notice any changes in their breasts they should see their GP.

Should women with dense breasts be screened more frequently?

Currently the best way for asymptomatic women aged 50-74 to detect breast cancer early is to have two-yearly screening mammograms through BreastScreen Australia.

BreastScreen Australia constantly monitors and reviews evidence to ensure the program is delivering safe, high-quality and evidence-based care to women. The program will continue to assess the evidence about assessing and managing women with dense breasts in the context of population based screening. However until there is more robust, scientific evidence available, two-yearly mammography is the most effective screening test for asymptomatic women aged 50-74 years, regardless of breast density.

Should women with dense breasts have any additional tests?

Currently there is no evidence that additional tests are warranted for women with dense breasts.[xvi] Extra screening tests may be considered by an individual woman and her doctor. Some possible options include ultrasound, Magnetic Resonance Imaging (MRI) and digital mammography tomosynthesis (3D mammography). However, there can be significant harms associated with having additional tests including unnecessary and invasive procedures, false positive results [xvii],[xviii] (a woman is told she has cancer when there is no cancer present), overdiagnosis, over-treatment, additional costs to both the woman and the health system and psychological distress.

Is BreastScreen Australia planning to report on breast density in the future?

BreastScreen Australia supports greater discussion, public awareness and research into breast density. BreastScreen Australia respects a client’s right of access to their personal medical information and encourages the involvement of clients in developing evidence-based approaches to breast cancer risk assessment, prevention and early diagnosis. The benefits and drawbacks of routine reporting of breast density are a complex issue that needs to be evaluated, in discussion with the consumers.



[i] Mousa, D., Brennan, PC., Ryan, EA., Lee, WB., Tan, J., and Mello-Thoms, C. (2014). ‘How mammographic breast density affects radiologists’ visual search patterns.’ Acad Radiology 12: 1386-1393

[ii] Kerlikowske, K., Grady, D., Barclay, J., Sickles, E.A., and Ernster, V. (1998). ‘Effect of age, breast density, and family history on the sensitivity of first screening mammography.’ JAMA 276 (3): 33-38

[iii] Sprague, B. L., Gangnon, R. E., Burt, V., Trentham-Dietz, A., Hampton, J. M., Wellman, R. D., Kerlikowske, K., and Miglioretti. D. L. (2014). ‘Prevalence of Mammographically Dense Breasts in the United States.’ JNCI Journal of the National Cancer Institute 106 (10): dju255 DOI: 10.1093/jnci/dju255 http://aje.oxfordjournals.org/content/181/12/956.full

[iv] Ng, K-H and Lau, S. (2015). ‘Vision 20/20: Mammographic breast density and its clinical applications.’ Med Phys 42(12):7059-7077. doi: 0094-2405/2015/42(12)/7059/19

[v] American College of Radiology. (2013). ‘BI-RADS – Mammography.’ Retrieved from http://www.acr.org/~/media/ACR/Documents/PDF/QualitySafety/Resources/BIRADS/01%20Mammography/02%20%20BIRADS%20Mammography%20Reporting.pdf 

[vi] Sprague, B.L., Stout, N.K., Schechter, C. et al. (2015). ‘Benefits, harms, and cost-effectiveness of supplemental ultrasonography screening for women with dense breasts.’ Ann Intern Med. 162(3): 157-66.

[vii] Kerlikowske K, Ichikawa L, Miglioretti DL, et al. Longitudinal measurement of clinical mammographic breast density to improve estimation of breast cancer risk. J Natl Cancer Inst 2007; 99:386-395

[viii] Baglietto, L., Krishnan, K., Stone, J., Apicella, C., Southey, M., English, D., Hopper, J., & Giles, G. (2013). ‘Associations of Mammographic Dense and Nondense Areas and Body Mass Index With Risk of Breast Cancer.’ American Journal of Epidemiology. Doi: 10.1093/aje/kwt260

[ix] Smith RA, Duffy SW, Gabe R, Tabar L, Yen AM, Chen TH. (2004). ‘The randomized trials of breast cancer screening: what have we learned?’ Radiol Clin North Am 42(5): 793–806

[x] Fry, R. (2001). ‘HRT makes mammography less effective.’ ABC Science Online. Published Friday 12 January 2001. Retrieved: http://www.abc.net.au/science/articles/2001/01/12/232048.htm?site=science/Askanexpert&topic=latest

[xi] Boyd, N., Guo, H., Martin, L., Sun, L., Stone, J., Fishell, E., Jong, R., Hislop, G., Chiarelli, A., Minkin, S., and Yaffe, M. (2007). ‘Mammographic Density and the Risk and Detection of Breast Cancer.’ The New England Journal of Medicine 356(3): 227-236

[xii] McCormack, V.A. and dos Santos Silva, I. (2006). ‘Breast Density and Parenchymal Patterns as Markers of Breast Cancer Risk: A Meta-analysis.’ Cancer Epidemiol Biomarkers Prev

[xiv] Australian Institute of Health and Welfare. (2009). BreastScreen Australia Evaluation Final Report.

[xv] Australian Institute of Health and Welfare. (2009). BreastScreen Australia Evaluation Final Report.

[xvi] American College of Radiologists. (2012) ACR Statement on Reporting Breast Density in Mammography Reports and Patient Summaries, April 24, 2012. Retrieved from http://www.acr.org/About-Us/Media-Center/Position-Statements/Position-Statements-Folder/Statement-on-Reporting-Breast-Density-in-Mammography-Reports-and-Patient-Summaries

[xvii] Siu, AL. et al, Screening for Breast Cancer: U.S. Preventive Services Task Force Recommendation Statement. Ann Intern Med 2016; 164: 279-296.

[xviii] Melnikow JM, Fenton JJ, Whitlock EP, et al. Supplemental Screening for Breast Cancer in Women With Dense Breasts: A Systematic Review for the U.S. Preventive Services Task Force. Agency for Healthcare Research and Quality, Rockville, MD, 2016. 

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