What we know about breast density as a risk factor for breast cancer

July 14th, 2017

As we know more about the causes of breast cancer, it’s becoming clear that it’s not only faulty genes and lifestyle factors that are to blame. ‘Breast density’ is also becoming a familiar phrase for those talking about who is at risk of developing breast cancer.

We know that an Australian woman has a 12.5 per cent chance of getting breast cancer in her lifetime.

Almost 8% of women aged between 40 and 74 years have extremely high breast density which puts them at a 50-70 per cent higher risk of developing breast cancer compared to women with low breast density.

To put that into perspective, around 5 per cent of breast cancers are caused by an inherited BRCA1 or BRCA2 gene fault. Recent research shows that a BRCA1or BRCA2 mutation puts women at a 69-72 per cent higher risk of breast cancer.

How to tell if you have dense breasts

Breast density isn’t the same as having firm breasts and isn’t based on how your breast feels. A mammogram is the only way to tell if a woman has dense breast tissue.

Breasts are made up of glandular tissue (milk-producing lobules and milk ducts), fibrous tissue and fat– the proportions of these change from woman to woman. Those with more fibrous tissue and less fat are considered dense. Breast density is very common but often reduces as women get older.

Mammograms and breast density

Regular mammograms are proven to save lives by detecting breast cancers early when treatment is more effective.

On a mammogram dense breast tissue appears white or bright while non-dense breast tissue appears dark. The problem is that breast cancers also appear white on a mammogram so having high breast density can mask or hide the cancer. This makes early detection more difficult as a tumour might be present and not picked up.

breast density mammogram


Research is helping women with high breast density

As more becomes known about breast density as a risk factor, researchers are using this knowledge to prevent women developing breast cancer. The National Breast Cancer Foundation is funding research which takes women’s breast density into account in models of screening programs of the future.

As mammograms do not have the sensitivity to distinguish between dense breast tissue and potential tumours, Professor Martin Ebert is turning to engineering principals to reimagine how tumour detection could work. His innovative no-harm, no-touch screening method has the potential to successfully identify cancerous tissue from healthy tissue regardless of the density of the breast.

A woman’s risk of breast cancer is made up of a complex set of factors – some she has control over and some she doesn’t. A more comprehensive screening program could include factors such as family history, smoking, overall health and breast density to name but a few. Dr Jocelyn Lippey is investigating how this type of risk assessment and screening would be delivered and received, potentially paving the way for a more tailored service for women.

Dr Jennifer Stone
Dr Jennifer Stone is researching better screening for dense breast tissue and cancer

Not all women are told at the time of their mammogram about their breast density because more information is needed to determine the best way to incorporate it into public health programs. Dr Jennifer Stone is conducting a trial to determine the impact of advising women of their breast density. She is also trying to determine the prevalence of dense breast tissue in Aboriginal women and young women to help improve public health for these women.