Dense breast tissue is normal and very common. About 40% of women 40 and older have dense breast tissue. It tends to run in families. The density of the breast is based on the proportion of stromal and epithelial tissue compared to fibrofatty tissue. For these women it makes it harder to interpret mammograms. Women with dense breasts are up to twice as likely to develop breast cancer as women with average density breasts. Possibly because dense tissue has more cells that can become abnormal, or women with dense breasts may have higher levels of estrogen.
Now there is an add-on cancer check for dense breast tissue known as a 3D whole-breast ultrasound tomography system. It sends sound waves to create a 360-degree image of the breast that offers a more comprehensive look at the tissue and details of any changes.
The Automated Breast Ultrasound (ABUS) is a newer approach to finding up to 30% more cancers in women who have dense breasts. With 3-D ultrasound volume and U-Systems software, radiologists can review hundreds of breast tissue image “slices”: to look at layers of breast tissue to find cancers which may have been missed by mammogram. There is no radiation with ultrasounds. The scan takes about 60 seconds and the technologist follows the display monitor in real time to make sure the entire breasts are covered. Usually 3 scans are performed on each breast.
Traditional ultrasounds are still done by ultrasound technicians and physicians. The limitations are that it is dependent on the skill of the operator and type of device used. There is also a shortage of ultrasound technicians. Sensitivity and specificity have been a problem. Whereas, the ABUS technique is a dedicated method that scans the breast in an automated, standardized manner with a transducer that is larger than that used in conventional ultrasound. Also, it does not need to be performed by a physician. Radiology technicians perform the procedure which allows physicians time to interpret their images.
Limitations related to the ABUS are that lesions behind the nipple and peripheral lesions may be missed (on the outside of the breast and under the arm), especially in women with large breasts. There can be artifacts due to poor positioning. There is a lack of studies evaluating ABUS use in women with breast implants as well as women who experience post operative changes such as scarring. If something looks “suspicious” a hand held ultrasound is used for further evaluation. In a 2020 study, the system measured breast tumor changes early in chemotherapy -which makes this potentially useful for evaluating if treatment is useful or not.
ABUS has a detection rate for invasive breast cancers that is equivalent to hand-held ultrasound when they are both used as a supplement tool to mammogram. Health plans are now required to cover regular screening mammograms without charging anything out of pocket. But that is not the case with supplemental screening for women with dense breasts. And theses tests can be pricey with on average breast ultrasound costing $250 out of pocket and a Breast MRI costing $1084 according to the Brem Foundation to Defeat Breast Cancer.
If you have extremely dense breast tissue, the detection rate of your screening mammogram is 70-75%. So there is a 25% chance that a cancer could be missed with just a mammogram.
Only 38 states require breast imaging centers to inform women of their breast density. Breast density is classified based on the Breast Imaging-Reporting and Data System (BI-RADS) of the American College of Radiologists. Density is classified into 4 categories:
A: All fatty Tissue, B: Mixture of scattered glandular and fatty tissue, C: Heterogeneously Dense Tissue, D: Extremely Dense Tissue. If you have heterogeneously dense breast tissue, the detection rate of your screening mammogram is around 80-85%. So there is a 15% chance that a breast cancer could be missed by mammogram along. By adding a diagnostic bilateral breast ultrasound to your mammogram, you increase your detection rate by 95%.
If you have extremely dense breast tissue, the detection rate of your screening mammogram is 70-75%. So there is a 25% chance that a cancer could be missed with just a mammogram. By adding a diagnostic bilateral breast ultrasound, you increase your cancer detection rate to 95%. Your breast density type is determined by your radiologist.
One key harm that researchers are concerned about, besides the possible extra cost, is the chance of a false-positive result. This could lead to follow-up testing such as breast biopsies that are invasive and raise cancer fears.
If 1000 women with dense breasts get an ultrasound after a negative mammogram, the ultrasound will identify 2-3 cancers, studies show. But the extra imaging will also identify up to 117 potential problems that leads to recall visits and testing that ultimately are a false positive. This can lead to lots of cost and emotional stress. This is why it is worth having a conversation with your practitioner on whether additional testing is worth it, especially for the 8% of women who have extremely dense breasts.
Studies have shown that mammograms reduce breast cancer mortality. But research has found that women that do more testing such as ultrasound or MRI are not less likely to die of breast cancer after a negative mammogram result. It’s best to discuss screening strategies with your practitioner. Options include 3D X-ray mammography, Ultrasound and an MRI along with a standard mammogram.
Reference: The George Washington University Hospital. Automated Breast Ultrasound System (ABUS). gwhospital.com
Andrews, M. Despite Katie Couric’s Advice, Doctors Say Ultrasound Breast Exams May Not Be Needed. KFF Health News, 10/2022.
Palmer, W. The Advantage of ABUS vs. Hand-Held Ultrasound with Dense Breasts. Diagnostic Imaging. Jan 29, 2020.
AARP The magazine: Medical Breakthroughs in Women’s health: 3D Ultrasound for better Mammograms. Oct/Nov 2023, p. 48-49.