Beyond the Mammogram
As a breast imager, I see thousands of patients’ mammograms every year. All are different from each other; some breasts are large, some are small. Some are round, some are thin. In mammography, those differences don’t really matter that much. We are still able to find breast cancers and find them early even with these differences and even before the patient or the doctor can feel them. But there is one single anatomical characteristic of the breast that does influence how accurately we can interpret the mammogram and that is Breast Density.
Breast density is unique to each woman. It is not something that you can just decide upon and/or change. It is a description of the amount of fat vs fibroglandular tissue (the actual tissue that conforms the breast gland) in the breast. When we interpret a mammogram, we are looking at images in black and white. Breast tissue is white in the mammogram while fatty tissue is black. The problem is that many of the abnormalities that show up in a mammogram and almost invariably all cancers are also white. If we take a white abnormality and put it over a white background it will lose its contrast and will be very difficult to differentiate from the normal background. See the example below:
As you can see, the star is easier to spot on the image on the right, since there is no white background. As the amount of the white increases, it becomes almost impossible to be seen.
Now lets see that on real mammograms. Breasts that are black on mammography are composed mostly of fat and are described in the report as fatty. At the other end of the spectrum, extremely dense breasts, which have a higher amount of fibroglandular tissue compared to fat are mostly white.
The higher the density, the higher the possibility obscuring abnormalities in your breasts, thus, decreasing the accuracy of the mammogram. Our mammography reports are usually sent to your primary doctor, and unfortunately, not all understand the importance of the breast density and might not discuss it with you.
In recent years, notifying patients of their dense breasts has become a law in several states in the USA, thanks to the advocacy of women who unfortunately where part of those patients where the cancer couldn't be seen on their mammogram given their density. You can read more about this here: https://www.areyoudense.org/.
It is important to know your breast density, not only because it has implications on the interpretation of the mammogram but also because having dense breasts also carries an increased risk of breast cancer.
Is there an option for these patients? Absolutely. Tomosynthesis or 3D mammograms can see the breast tissue through 1 mm slices, making the differences between abnormalities and the background more noticeable for us. An ultrasound, which is a comfortable test that involves no radiation is also a great supplemental option to add to your screening mammogram. MRIs are also helpful, especially in women who have a high risk of breast cancer (family history, genetic mutations, etc).
An ultrasound, which is a comfortable test that involves no radiation is also a great supplemental option to add to your screening mammogram. MRIs are also helpful, especially in women who have a high risk of breast cancer
Many patients will ask: “so if I have dense breasts, why would I need a mammogram? Why not get an ultrasound only?” and it is a valid question. However, mammograms are still important and necessary because certain cancers (and some very early cancers) only show up in the mammogram and would not be seen under ultrasound. You don’t want to miss these!
Your breast health is your responsibility. Once you know you have dense breasts, be proactive! Get your mammogram (better if it is 3D) every year but also know when the mammogram might not be enough: ask your doctor to send you in for a supplementary screening modality such as an ultrasound or MRI. There is more to know beyond the mammogram.
Dr. Claudia Cotes is a Radiologist specialized in Breast Imaging at The Rose, a non-profit organization that provides breast imaging and diagnostic services for underserved women in Houston