Understanding breast density.

Since dense breasts can actually obscure a lump on a standard mammogram, knowing the density percentage of the breasts will let you consider personalised screening options.

Health Care Professionals

1. How do I know if I have dense breasts?

Breast density is seen only on mammograms.1 Dense breasts have a lot of fibrous or glandular tissue and less fatty tissue.1 Breast density may be included in the report from the radiologist following a mammogram so you can ask your doctor about your breast density.

2. Is breast size related to breast density?

You may be surprised to learn that breast density isn’t based on how your breasts look or feel e.g. the size or firmness.1 In fact, breast density is seen only on mammograms.1 Breast density relates to the type of tissue present, not to the size or firmness. Dense breasts have a lot of fibrous or glandular tissue and less fatty tissue.1 While you can’t tell whether your breasts are dense from looking at them or feeling them, it is still important for each woman to know the normal look and feel of her breasts. If you notice any changes in your breasts, you should visit your GP.

3. Who is more likely to have dense breasts and can I change my breast density?

Breast density is often greater in women who are younger.1 Other factors that may increase the likelihood of having dense breasts include being pre-menopausal, use of certain drugs such as menopausal hormone therapy, being pregnant or lactating and as a result of genetics.1 While some women’s breasts become less dense with age, others experience little change.1 In general, the best way to deal with the increased risk associated with having dense breasts is not to try to reduce your breast density, but to talk to your doctor about a breast cancer screening program that suits your individual needs.

4. What does it means for me in terms of breast cancer screening if I have dense breasts?

Standard 2D mammograms may be less accurate in women with dense breasts.2,3 3D mammography is a newer technology that helps to eliminate most detection challenges associated with standard 2D mammography in a diagnostic setting.4,5 3D mammography has been shown to detect approximately 40% more invasive breast cancers and reduce the need for unnecessary further testing by up to 40%. This means two simple things: earlier detection than ever before and less anxiety about unnecessary further testing.4,5

3D mammography may be performed in conjunction with an ultrasound and/or MRI exam. Breast ultrasound uses sound waves to create a computer image of the inside of the breast.6 It is particularly useful in younger women with dense breasts.1,6 Ultrasound is frequently used to compliment mammography and can often tell the difference between benign (non-cancerous) findings and solid masses (which may need further testing to check whether they are cancer).5 Ultrasound does not involve radiation exposure so is the preferred first option in women who are pregnant or breastfeeding.1

Breast MRI (magnetic resonance imaging) is another imaging option that may be useful in women with dense breasts.1 It uses strong magnets instead of radiation to make very detailed, cross-sectional images of the breast.1 MRI is very good at detecting cancer but it is also more likely to find suspicious changes that turn out not to be cancer (called a false positive).1 MRI is recommended as a screening test in younger women at high risk.

References: 1. American Cancer Society. Available at: https://www.cancer.org/cancer/breast-cancer/screening-tests-and-early-detection/mammograms/breast-density-and-your-mammogram-report.html. Accessed November 2017. 2. Skaane P et al. Radiology 2013;267:47–56. 3. Friedewald S et al. JAMA 2014;311:2499–507. 4. Rose S et al. AJRAm J Roentgenol 2013;200:1401–8. 5. Australian Institute of Health and Welfare 2013. BreastScreen Australia monitoring report 2010– 2011.Cancer series no. 77. Cat. no. CAN 74. Canberra: AIHW. 5. American Cancer Society. Breast ultrasound. Available at: https://www.cancer.org/cancer/breast-cancer/screening-tests-and-early-detection/breast-ultrasound.html. Accessed November 2017. 7. Cancer Australia. The investigation of a new breast symptom: a guide for general practitioners. February 2006. Available at: https://canceraustralia.gov.au/sites/default/files/publications/ibs-investigation-of-new-breast-symptoms_50ac43dbc9a16.pdf. Accessed March 2016.

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