Having Dense Breasts: A Clear Risk Factor for Breast Cancer

What is Breast Density?

Breasts are made up of fatty tissue and fibroglandular tissue (including glands that make milk, held together by fibrous tissue). On a mammogram – an x-ray of the breast – fibroglandular tissue appears white and fatty tissue appears dark. The white areas are referred to as breast density.

There are four categories to classify breast density:

* A: almost entirely fatty
* B: scattered areas of fibroglandular density
* C: heterogeneously or consistently dense
* D: extremely dense

Breast density is very common. Around 40% of women aged 40–74 are estimated to have “dense breasts”, meaning they fall in category C or D.

What’s the Link to Cancer?

Breast density is associated with the risk of breast cancer in two ways.

First, breast density usually decreases with age. But if a woman has high breast density for her age, it increases her likelihood of breast cancer.

Second, breast density “masks” cancers if they develop. Both cancers and breast density appear white on a mammogram, making cancers very hard to see.

What’s the Current Advice?

In Australia, advice for women with dense breasts and their health-care professionals can be inconsistent and confusing.

* The Royal Australian and New Zealand College of Radiologists recommends breast density is recorded during screening and diagnostic tests in Australia and New Zealand.
* BreastScreen Australia says it “should not routinely record breast density or provide supplemental testing for women with dense breasts”. However, this position statement is from 2020 and is currently under review.
* Some state and territory BreastScreen programs, including in Western Australia, South Australia, and soon Victoria, notify women if they have dense breasts. Victoria is currently at an early stage of its roll-out.

What are the Issues?

Providing recommendations for women with dense breasts is difficult.

* The European Society of Breast Imaging recommends women with extremely dense breasts aged 50–70 receive an MRI every two to four years, in addition to screening mammography. However, the Royal Australian and New Zealand College of Radiologists describes this recommendation as “aspirational”, acknowledging cost, staffing, and accessibility as challenges.
* There is no consensus on appropriate screening recommendations for women in category C (heterogeneous density).
* We need a national approach to breast density reporting in Australia and to do better at identifying who is most likely to benefit from further testing.

Conclusion

Breast density is a clear risk factor for breast cancer. While the messaging regarding breast density differs by state, none currently recommend further imaging for women with dense breasts without speaking to a doctor about individual risk. A national approach to breast density reporting in Australia is needed to enable a consistent approach to breast screening practices.

FAQs

* What is breast density?
Breast density is the proportion of fibroglandular tissue in the breast.
* What is the link to breast cancer?
Breast density is associated with the risk of breast cancer. High breast density for age increases the likelihood of breast cancer, and breast density can mask cancers on a mammogram.
* What is the current advice for women with dense breasts?
The advice is inconsistent and confusing, with different recommendations from different organizations and states.
* What are the issues with providing recommendations for women with dense breasts?
The issues include the lack of consensus on appropriate screening recommendations, the high cost of MRI, and the need for a national approach to breast density reporting in Australia.