My sister was recently diagnosed with breast cancer at age 57. This completely blind-sided us as we do not have a family history of breast cancer. Fortunately, the cancer was picked up during her regular 2 yearly screening mammogram, was biopsied and removed in around 6 weeks.
Through this experience however, I was suddenly no longer the practitioner and researcher, but the cheer squad my sister needed. I felt able to reassure her that because it was found early, she will live a long and happy life.
Two things that really stood out to me upon this journey was that thanks to my sister’s proactivity, attending her regular screening appointments the cancer was detected early. But as a researcher in the area of breast density, the element that shone brightest was that due to her fatty breast tissue, her 9mm cancer was relatively easy to detect by a radiologist.
So, what is breast density, and why does it matter?
Breast density refers to the level of normal glandular tissue that is present in a breast. As a women ages, it is common for the glandular tissue to be replaced by fatty tissue. Hence, they are less firm. However, this is not always the case with high levels of dense tissue persisting into the post-menopausal years.
A good way to think about density is imagining that the sun is a mass and the clouds are dense tissue on a mammogram. These ‘clouds’ block out or mask pathology, which makes it incredibly difficult for a radiologist to diagnose from 4 views. Whereas, a fatty breast (less dense) is like looking into a clear sky.
The reasons that women with dense breasts are at a higher risk of cancer are twofold; simply having more tissue means there is more areas for cancer to grow, and studies show that radiological cancer detection is reduced by density. From a clinical viewpoint, it would seem reasonable to inform women and their clinicians about their density levels, so that appropriate and personalised care can be directed. For instance, in the case of a dense breast, further imaging modalities such as digital breast tomosynthesis, ultrasound or magnetic resonance imaging may be required to reach a definitive diagnosis.
Current breast screening reporting protocols in Australia do not include a mammographic density rating. However, for almost half of the United States, density scoring is mandatory and legislation is coming in for all states soon.
Density can be recorded in the report using a similar standardised system for the normal/abnormal distinction. The radiologist assigns a density score that varies on a scale from 1 (fatty), 2 (scattered fibroglandular), 3 (heterogenously dense) to 4 (extremely dense). One of the issues with this system is that studies have shown that the coding system is highly subjective. One way around this is designing a density coding system which uses artificial intelligence. Recently, a group at Harvard University developed a deep-learning algorithm to perform this essential task.
Is a mammogram enough to detect my breast cancer?
Mammograms are a great tool to detect breast cancers, however are not fool-proof. Often, mammogram reports can be confusing, especially if you have anything unusual that shows up.
However, it is important that everything is documented, so that you and your doctor are armed with information. Sometimes this information can be overwhelming, or a concern arises, because clarification is needed via further views or a follow-up test like ultrasound. Most of the time, this clarification shows that the breasts are indeed normal. In a screening environment, the reporting occurs up to 2 weeks after the mammogram is taken and it is not uncommon for a radiologist to request more views.
Radiologists are the doctors who report the mammogram; the radiographer is the technician that acquires the image – and the one you hate for around 1 minute (although I can personally vouch for the fact that the newer, digital systems are less painful). A radiologists’ role is a challenging one, especially in a screening environment. They are required to search through a cluttered image and make diagnostic decisions based on 4 views only (2 each side).
What does the report mean?
Often a radiologist will report the findings according to a standardised protocol. For example, using a Breast Imaging and Reporting Data System (BIRADS: American College of Radiology: Breast Imaging Reporting and Data System Atlas. Reston, Va: © American College of Radiology, 2003). BIRADS is a standardised breast assessment tool developed for mammography that ranges from 0 to 6. In clinical practice, a radiologist assigns a BIRADS score to each image, which determines the next step in the diagnostic protocol. The codes range from 1 to 6 with one being no significant abnormality, 2 (benign), 3 (probably benign), 4 (suspicious abnormality and biopsy recommended), 5 (highly suggestive of malignancy), to 6 (known pathological proven malignancy).
If I’m not told of my breast density, what questions should I be asking, how can I find out more?
As mentioned, in Australia, you are unlikely to learn your breast density unless you have been called back from a screening mammogram. However, I believe this will soon change.
Next time you see your GP, have a discussion about the ways to learn about your breast density. If you find you have dense tissue, you may choose to have a 3D mammogram also known as breast tomosynthesis, which is more sensitive for cancer in a dense breast. A breast tomo takes views from different angles and then computes into a scan like a CT which the radiologist ‘scrolls’ through. In the case of strong family history, or a previous cancer, clinicians will refer you for an MRI of the breast. Even though this is considered the ‘gold standard’ of breast cancer detection in a dense breast, it is very expensive, and not claimable through Medicare in a screening scenario. You can, of course opt to pay yourself.
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