A week or so after your latest mammogram you may receive a letter from the imaging facility. “Your mammogram demonstrates that you have dense breast tissue,” begins the letter sent to women in Virginia. “[This] is very common … However, [it] can make it harder to find cancer on a mammogram and may also be associated with an increased risk of breast cancer.”
Dense breasts? An increased risk of cancer? Naturally, your hands may fly to your chest to feel for something obvious. But density can only be detected on a mammogram, which produces black-and-white X-ray images:
- Dark gray areas show fatty (non-dense) tissue.
- White areas show non-fatty (dense) tissue.
Radiologists evaluate the balance of dark-to-light tissue. Your results will be assigned one of the following categories:
- Almost entirely fatty: About 10% of women fall into this category.
- Scattered with areas of dense tissue: About 40% of women have this type of tissue on mammogram.
- Heterogeneously dense: Most of your breast tissue is dense. About 40% of women are in this category.
- Extremely dense: About 10% of women have breast tissue that is almost all dense.
Dense breast tissue can conceal tumors and other abnormal changes, which appear light-colored on mammograms. The denser the tissue, the greater the risk of breast cancer going unnoticed. Women living in Virginia are notified via letter if their mammogram shows heterogeneously or extremely dense breast tissue.
What Should I Do With This Information?
“Two advanced screening techniques are of clear value to women with dense or extremely dense breasts,” says Dr. Jennifer Harvey, professor of radiology at the UVA School of Medicine:
Screening Breast Ultrasound
As opposed to radiation, breast ultrasound uses sound waves to generate a computer picture of breast tissue. This test may increase the risk of a false-positive result, meaning it frequently detects both non-cancerous (benign) and cancerous growths. About 7% of women who have a screening ultrasound are then referred for a biopsy and most of these will be benign. Breast ultrasound can detect up to 30% more breast cancers than a mammogram, even after a screening mammogram has been read as normal.
This newer type of mammogram takes multiple pictures of your breast, from several different angles, to produce 3-D images. The type of imaging is similar to a regular mammogram but with the addition of a small X-ray device that sweeps above your breast to gather additional images. Tomosynthesis can detect up to 30% more breast cancers than regular mammograms. The study involves slightly more radiation than a regular mammogram but is associated with a lower false-positive rate than breast ultrasound and regular mammograms.
“Most women could benefit from both of these additional screenings,” Dr. Harvey says, “but if you must choose, women with extremely dense breast tissue are likely to benefit more a breast ultrasound than tomosynthesis.”
Women with heterogeneous breast tissue should consider alternating yearly between tomosynthesis and breast ultrasound, in addition to their regular mammograms, says Dr. Harvey.
Log on for Your Detailed Mammogram Results
If you’re a patient in the UVA system, you can log into MyChart to see your full mammography report and a summary of your personal lifetime risk of breast cancer.
UVA's dedicated breast radiologists can answer your questions about dense breast tissue and help you make informed decisions about additional screening tests.Learn More