After undergoing a risk-reducing mastectomy earlier this year, Sandy Minck doesn't mince words.
"For me, having watched my mother die of breast cancer and having all these risk factors, the decision was easy," she says.
With a family history of breast and ovarian cancer, and a genetic mutation that makes her more predisposed to developing the disease, Dr Minck knows better than most the importance of understanding breast health in all of its complexities.
But after undergoing screening at a private clinic, she was surprised to discover that she also has "extremely dense breasts"; a condition affecting about 10 per cent of women.
It's not related to breast size, nor can it be determined by touch or feel — and there's debate over whether women should know about it.
For a small proportion of women like Dr Minck who have dense breasts, it can carry a heightened risk of developing cancer, and make it harder to identify issues during routine screening.
But for most women, it's unlikely to have any real bearing on their breast health, and there are fears from some within the medical sector that telling women about their breast density could create undue anxiety.
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What are 'dense breasts'?
Don't worry, it's not a silly question.
Your breasts are made up of three key components: fatty tissue, glandular tissue (like the milk ducts and lobules), and connective tissue, which helps hold everything together.
You can't see or feel these in a clinical exam, but a mammogram can help measure and compare the different types of breast tissue. You can learn more about what it looks like in the charts below.
Radiologists are able to use this to score breast density on a scale from very low density to mostly dense.
Here's a breakdown courtesy of the American College of Radiology’s Breast Imaging Reporting and Data System (otherwise known as BI-RADS).
Why does breast density matter?
Women with heterogeneously or extremely dense breasts have a higher risk of developing breast cancer than women with fattier breasts.
As you can see from the slider below, dense breasts can also make a mammogram more difficult to interpret.
Cancers can be masked by the glandular and connective breast tissue, which all show up as white on a mammogram (compared to fatty tissue, for example, which appears as dark areas).
Because of this, breast density can be used as "a predictor of what we call the interval cancer", explains John Hopper, a professorial fellow at the University of Melbourne.
"That's when you have a mammogram and you're given the all clear, and then in the interval before the next screen, the woman has a lump or whatever and it's diagnosed as a cancer," he says.
"They tend to be nastier than screen-detected cancers."
What does it mean if I have dense breasts?
Breast density — and how much it can and should be used to predict the likelihood of developing cancer — remains a contentious topic.
But if there's one thing the experts all agree on, it's this: don't freak out.
"I don't think there's a quantifiable risk yet of exactly how much increased risk you're at of breast cancer if you have dense breasts, just because there's so many other risk factors," says Dr Alia Kaderbhai, chair of the RACGP Specific Interests Breast Medicine network.
It's a sentiment echoed by Professor Hopper, who says that while some women may fall into the higher density category, advancements in testing have found it's only "really a problem" in about the "very extreme" one per cent.
"My analogy is driving a car with faulty brakes — if you leave and the weather's fine and there's not much traffic around, you can get away with it," he says.
"But once something starts to happen that puts you at risk, such as your environment changes or your underlying risk factors change because of bad weather and things like that, suddenly having faulty brakes is a real problem.
"And that's the way to think about density. Density on its own is not really the major problem, it's density and risk."
What factors influence breast density?
Risk is a concept Dr Minck understands all too well.
After losing her mother to cancer and witnessing her grandmother be diagnosed with ovarian cancer, she decided that "knowledge is power" and pursued further breast screening at her own cost.
An MRI ultimately resulted in the excision of a tumour in her milk glands known as a lobular carcioma in situ, while genetic testing revealed that she carried the CHEK2 gene, a genetic mutation that increases the risk for some types of cancers.
"Then I got my dad tested, and [the gene mutation] came from that side of the family," Dr Minck says.
"So I think in my situation, the likelihood is that I inherited my extremely dense breasts from my mother and the genetic mutation from my father."
When it comes to breast density, genetics are an unavoidable factor. It's largely determined when the breasts first form, and that means that some women will always sit in a high-density category compared with others their age.
However, there are a range of other factors that play a role.
Paradoxically, while factors like a lower BMI can lead to increased breast density, being leaner is also known to reduce the risk of developing cancer more broadly, says Dr Kaderbhai.
"I think you have to weigh up all these things when you're thinking about risk," she says.
"So I think it's just about looking at the whole picture, not breast density alone."
Should women be told if they have dense breasts?
Last year, the European Society of Breast Imaging released a recommendation that women with extremely dense breast tissue should be offered screening with breast MRI, which it said could "reduce the mortality from breast cancer and is highly cost-effective".
While there is currently no consistent protocol in Australia to measure and report breast density, some states have taken steps to notify women of their status.
In Western Australia, for example, women whose mammograms show marked increased breast density are advised in writing to consult their GP, while BreastScreen SA is conducting a research study into "measuring and reporting individual breast density for clients".
Though work is underway on a smaller scale, when it comes to whether women more broadly should be informed about their breast density, patients and doctors alike are divided.
On the one hand, "we don't quite understand the implications of breast density alone", notes Dr Kaderbhai, who believes that telling women they've got dense breasts "is more likely to increase anxiety amongst women with little improvement in outcome".
"I think before we start to report these things, we really need to understand how to communicate it to the patient accurately, what implications that has, and what advice to give them," Dr Kaderbhai says.
"Once you start reporting these things on the mammogram reports, patients are going to come back to their GP and say, 'Well, what do I do about this?' And if we can't give them an answer, you're just creating a large pool of women with anxiety and nowhere to go with it."
For Dr Minck, who sought out further screening to develop a better understanding of her own risk factors, the notion that having access to this information could cause distress "just really goes against the grain for me".
"Women need to know about risks," she says: "Even if we don't know exactly what to do with that information".
"The other concern is over diagnosis. So obviously, the more investigations you do, the more you're going to find, the more tests you're going to need to do," Dr Minck says.
"But every woman I've spoken to has said they would rather have a false positive, than have their cancer missed, and they would rather know this information so that they can take action."
Pointing to the potential of AI algorithms to help automate data, Professor Hopper believes change is on the horizon.
He says researchers are "learning how to measure density" in a way that is consistent, which could help bolster future management of people who have dense breasts.
"So when a woman comes to have a mammogram, the assessment of her risk based on a mammogram and her risk based on her density can be automatically generated, because it's digital," he says.
"We want to work out how to combine that information to then give the woman the best management by the radiologists and the best management in terms of future screening and any other things that she might want to consider."
So what should you do if you have dense breasts?
Density is one of a number of wider risk factors, and mammograms remain the recommended screening tool.
"Women who are concerned about about their breast cancer risk should chat to their GP about their breast cancer risk as a whole and the topic of breast density can come into that," says Dr Kaderbhai.
Anyone with very high breast density and other risk factors can discuss supplementary screening options, "which could include contrast-enhanced mammography (CEM), ultrasound or MRI, with their GP", adds Kirsten Pilatti, CEO of Breast Cancer Network Australia.
Through Dr Minck's own experiences navigating the health system, she knows how challenging it can be trying to sort through all the information.
Above all, she says, it's important to know "what your breasts look and feel like", and to take advantage of risk assessment tools like iPrevent.
"Be breast aware, know your risks, advocate for yourself, and talk to your GP," she says.
