What does dense breast tissue mean? A guide to supplemental screening
Breast tissue density is a critical factor in cancer screening. During our recent webinar with University of Pittsburgh Medical Center breast imaging radiologist Dr. Amy Kelly, we discussed the significance of breast density, what it means if you learn you have dense breasts, and the additional imaging that’s potentially recommended. We’ve provided a recap of this topic transcribed from the conversation.
If you’d like to learn more about breast cancer guidelines and emerging advances in the field, the full webinar recording is available below.
The following questions and responses have been lightly edited for grammatical purposes.
1) I learned from my first mammogram that I have dense breasts. What does this mean?
Dr. Amy Kelly: Breast tissue density is so important. There was a federal law passed on September 10, 2024, that requires all mammograms to inform patients whether they have dense breast tissue or not, in language that they can understand, as well as [provide] the meaning of dense breast tissue. For example, we give all of our patients a letter after their mammogram that says either they have non-dense breast tissue or dense breast tissue.
This is important because almost half of women have dense breast tissue. Statistics show that about 40% of women, depending on their age, have dense breast tissue, and it’s important to be upfront, open, and honest with patients that mammography has a lower sensitivity in women with dense breasts. Cancers can be missed due to that, even with 3D tomosynthesis, because of the masking effect. Some women do benefit from supplemental screening, in addition to mammography, with ultrasound and MRI. The first step is to know whether or not you have dense breast tissue, and the second step is to have knowledge and understand what that means.
Cancer can be missed, so it’s important to know what to do about it. At our institution, for supplemental screening, we recommend breast MRI instead of ultrasound, and I always advise patients to talk with their doctor, referring provider, or radiologist about what’s specifically best for them.
We use breast MRI for supplemental screening because it has a higher cancer detection rate compared to ultrasound and it also has a lower false positive rate. For those two main reasons, we’ve really shifted toward breast MRI instead of ultrasound.
2) When should I get additional imaging?
Dr. Amy Kelly: So, when do we recommend a breast MRI? I like to think of it as a spectrum of cases. On one end, we have women with extremely dense breast tissue. That’s category D, if you’re familiar with the different categories of breast tissue. For these women, we recommend breast MRI as an addition to mammography, regardless of other risk factors.
On the other end, there are women at high, elevated risk for breast cancer, and we also recommend supplemental screening with breast MRI for them, regardless of their breast tissue density. These high-risk patients include women with a calculated lifetime risk of over 20%, those with a genetic predisposition to breast cancer, like the BRCA gene, or those who had chest radiation before age 30.
So we have women with extremely dense breast tissue [who are] getting an MRI, regardless of their risk, and we have high-risk women who are getting supplemental screening, regardless of their density. Then we have a broad category in the middle, which includes women who have dense breast tissue and some risk factors. That means women with heterogeneously or extremely dense breast tissue (categories C or D) and women with a family history of breast cancer. We’re also recommending it for women with a history of atypical lesions, such as LCIS or ADH.
For these three groups of women, supported by the Society of Breast Imaging and American College of Radiology recommendations, supplemental breast MRI in addition to mammography can be very beneficial. The timing can vary, but ideally we alternate every six months. So a woman would have a mammogram, then six months later an MRI, and then six months later her next annual mammogram.
The idea behind this is to detect any interval breast cancers, cancers that develop in the time between screenings. By alternating mammography and MRI every six months, we can catch interval cancers more effectively and we definitely do.
View part one of our webinar recap on mammography here.
