Because breast density influences both a woman’s cancer risk and the effectiveness of mammography, it’s essential to understand the implications of dense breast tissue and how to guide patients through appropriate supplemental screening. At Duke Health, breast imaging specialists personalize each patient’s screening plan with evidence-based risk assessment protocols.

“Breast density has deservedly gotten a lot of attention,” says Karen Johnson, MD, division chief of breast imaging at Duke Health. “Mammography is a great screening tool, but it has limitations, which are greater in women with dense breast tissue.”

Johnson points out that breast density can only be determined on a mammogram. Physical examination doesn’t identify breast density, and patients will not know their breast density until a mammogram is performed. On mammography, dense fibroglandular tissue appears white, while fatty tissue is dark or black. Breast cancer typically manifests as a mass, an asymmetry, and/or calcifications on a mammogram. Each of these findings also appear as a white density on a mammogram. Therefore, dense white breast tissue can mask the white density associated with a breast cancer making tumors more difficult to detect.

Federal regulations now require mammography facilities to also notify patients with dense breast tissue that dense tissue makes it harder to find cancer on a mammogram and also raises the risk of developing breast cancer. This messaging also advises that other imaging tests in addition to mammography may help find cancers.
Breast density classification is divided into four categories. The first two categories, predominantly fatty and scattered fibroglandular density, are considered non-dense, while heterogeneously dense and extremely dense breasts are categorized as dense.

In addition to masking cancers on imaging, dense breast tissue is also associated with a modestly increased risk of developing breast cancer. However, density alone does not typically place a patient in the high-risk category. While a woman’s breast density usually remains fairly consistent throughout her lifetime, Johnson explains that physiological changes from lactation and hormone replacement therapy (HRT) can increase breast density for periods of time.

Risk assessment models that incorporate factors such as age, family history, breast density, and reproductive history can help clinicians determine whether patients qualify for high-risk screening protocols. National guidelines recommend that women undergo a formal risk assessment by age 30. “Primary care and women’s health providers can play a big role by encouraging women to learn about their breast cancer risk early on, so they can get the right plan in place for screening,” Johnson notes.

For women with dense breast tissue and considered high risk, professional medical societies, including the American College of Radiology and the National Comprehensive Cancer Network, recommend discussing supplemental screening options.

At Duke Health, these options include screening breast ultrasound, breast MRI, abbreviated breast MRI, and, for some patients, contrast-enhanced mammography. “We have all of the modalities for supplemental breast cancer screening to provide the highest quality care to our patients,” says Johnson.

She adds, “MRI is far superior in terms of sensitivity and also has greater specificity than ultrasound. Ultrasound can be sensitive but less specific, which can lead to more follow-up imaging or biopsies.”

Cost and insurance coverage can be a barrier to breast MRI screening for some high-risk patients. To expand access, Duke offers an abbreviated breast MRI protocol designed for women with dense breasts who are at average risk. The abbreviated MRI is available at an out-of-pocket cost of $400, which can be much less than the cost of a traditional breast MRI, even with insurance coverage.

Duke Health’s Breast Imaging Division is closely integrated with its Breast Risk Assessment Clinic, enabling coordinated evaluation, screening, and continued care. “A lot of our patients will have their mammogram the same day they see a provider in the clinic,” Johnson says. “They often come to us first, so the provider already knows whether the imaging is normal or abnormal.”

Duke breast radiologists also frequently consult with referring primary care physicians and OB/GYNs to help guide screening decisions for patients with dense breasts. “We are always happy to talk to referring providers about their patients’ screening recommendations,” Johnson says. “Supplemental screening comes up often, and we’re available to help determine what’s in the best interest of a particular patient.”

At Duke Health, breast images are interpreted exclusively by breast imaging radiologists with specialized training and experience to interpret dense breast tissue. “I think it makes a difference who is reading your mammogram,” Johnson says. “All breast radiologists are working within the same digital platform, too, so we all have access to patients’ imaging from any Duke Health location.” 

If a patient does have suspicious imaging that requires additional imaging or a breast biopsy, the radiology team remains involved to ensure continuity of care. “All of our biopsies are image-guided and performed by our breast radiologists,” says Johnson. The program is also advancing research and clinical implementation of emerging technologies, including contrast-enhanced mammography, which combines standard imaging with physiologic information from intravenous contrast to highlight areas of increased blood flow associated with malignancy.

As breast density awareness grows among both clinicians and patients, Johnson believes informed screening discussions will become increasingly central to breast cancer detection. She says, “The key is helping women and their providers understand the options so screening can be personalized.”