For most women attending routine breast screening in the UK, the process is fairly straightforward. You attend for your mammogram, wait for the results letter, and hopefully receive reassurance that no abnormality has been identified.
However, one thing that is still not routinely discussed within the NHS Breast Screening Programme is breast density.
Over recent years, breast density has become a much bigger topic within breast imaging and cancer detection, and understandably more women are now asking questions about it. As a Consultant Radiographer, I see more women who want to understand what breast density actually means, whether it increases their risk of breast cancer, and whether they should be having any additional imaging because of it.
The reality is that breast density does matter, but it is also important that women receive balanced, evidence-based information rather than unnecessary anxiety.
What is breast density?
Breast density refers to the amount of fibroglandular tissue compared with fatty tissue within the breast. It is not related to breast size and cannot be determined by how the breast feels on examination. Breast density can only really be assessed on mammographic imaging.
On a mammogram, fatty tissue appears dark, whilst dense glandular tissue appears white. Unfortunately, breast cancers also usually appear white on mammography, meaning dense tissue can make cancers more difficult to see. This is often referred to as the “masking effect”, a well-established challenge in breast imaging research.
Breast density is usually divided into four categories using the BI-RADS classification system:
- A – Almost entirely fatty
- B – Scattered areas of density
- C – Heterogeneously dense
- D – Extremely dense
Women in categories C and D are generally considered to have dense breasts.
Why does breast density matter?
There are two main reasons why breast density is important.
Increased breast cancer risk
Firstly, breast density itself is recognised as an independent risk factor for breast cancer. Women with extremely dense breasts are thought to have a significantly increased risk of developing breast cancer compared with women with predominantly fatty breasts, as demonstrated in research on mammographic density and breast cancer risk.
That being said, breast density is only one factor that can influence a woman’s risk of developing breast cancer. Family history, genetics, hormonal factors, age and lifestyle all continue to play a role. Having dense breasts certainly does not mean a woman will develop breast cancer, just as women with non-dense breasts can still develop breast cancer.
Reduced sensitivity of mammography
From a screening perspective, arguably the more important issue is that dense breast tissue can reduce the sensitivity of mammography.
Because both dense tissue and cancers appear white on imaging, abnormalities can sometimes be hidden within the background glandular tissue. Recent research has shown that interval cancer rates increase significantly with increasing breast density, according to recent evidence on breast density and interval cancer risk.
This does not mean mammography is ineffective in women with dense breasts. Mammography remains an extremely valuable screening tool and continues to save lives. However, it does highlight that breast density is something we increasingly need to understand better.
What happens in the UK?
At present, women attending NHS breast screening are not routinely informed of their breast density following mammography, and additional screening purely based on breast density is not currently part of the NHS Breast Screening Programme, according to the UK National Screening Committee.
This differs from some countries internationally, particularly the United States, where breast density notification is now mandatory following mammography.
However, things are changing. There is increasing discussion within the UK regarding more personalised, risk-adapted breast screening pathways, and breast density is becoming a significant part of that conversation.
In 2022, the European Society of Breast Imaging recommended that women should be informed of their breast density and that supplemental MRI screening should be considered for women with extremely dense breasts, as outlined in the EUSOBI recommendations.
Emerging research and the BRAID trial
One of the most important recent UK studies looking at breast density is the BRAID trial, published in 2025.
The study investigated whether additional imaging techniques could improve cancer detection in women with dense breasts who had already had a normal mammogram, as reported by the Cambridge Biomedical Research Centre.
The trial assessed:
- Abbreviated MRI
- Contrast-enhanced mammography (CEM)
- Automated breast ultrasound (ABUS)
The findings were significant. Both abbreviated MRI and contrast-enhanced mammography detected substantially more cancers than standard mammography alone in women with dense breasts, according to the BRAID trial findings.
The study suggested that introducing supplemental imaging for women with very dense breasts could potentially identify thousands of additional cancers across the UK each year, allowing earlier diagnosis and potentially improving outcomes, as highlighted by Cancer Research UK.
From my experience working within breast imaging, I believe this is likely to be an area we will see develop considerably over the next decade.
Should women be worried?
In short, no, but awareness is important.
Dense breasts are extremely common, particularly in younger and pre-menopausal women. Many women with dense breasts will never develop breast cancer, and equally many breast cancers occur in women without dense breasts.
The important thing is understanding that breast density can affect both breast cancer risk and how well mammography performs.
Women should continue to attend routine screening appointments, remain breast aware, and report any new symptoms promptly, regardless of previous imaging results.
I also think it is important that we are honest with women that breast screening, whilst extremely beneficial, is not infallible. No imaging test is perfect, and breast density is one of the reasons why.
Final thoughts
Breast density is not something women can change, but it is something women should be aware of.
For me, the most important thing is education and informed choice. Women deserve access to clear, balanced information regarding their breast health so they can make informed decisions and understand both the benefits and limitations of breast screening.
I suspect breast density will become a much more routine part of breast screening discussions in the UK over the coming years, particularly as further evidence emerges regarding supplemental imaging and personalised screening pathways.
Ultimately, understanding breast density is not about causing fear. It is about improving awareness, improving early detection, and continuing to move breast screening forward in a way that best supports women and patient care.
Further reading
- Cancer Research UK: Dense breasts and enhanced breast cancer screening
- UK National Screening Committee review of breast density screening
- NHS breast screening: helping you decide
- Cambridge Biomedical Research Centre BRAID trial findings
- European Society of Breast Imaging recommendations on breast density and supplemental screening
