By Basak Dogan, M.D., Director of Breast Imaging Research, Department of Radiology, UT Southwestern Medical Center
When you get the results of your mammogram, you will see a section that refers to your breasts as “dense” or “not dense.” These terms have nothing to do with the look or feel of your breasts, and having dense breasts does not mean something is wrong. But knowing which category you’re in can impact how you should be screened for breast cancer.
About half of women over 40 have dense breasts. The denser the breast tissue, the more difficult it is to spot cancer on a standard mammogram. Having dense breast tissue can make it harder to detect cancer and sometimes leads to consideration of supplemental screenings along with your mammogram.
Since 2024, the Food and Drug Administration has required that mammography centers tell women whether they have dense breasts – something Texas health centers have done since 2012.
There are no symptoms related to dense breasts, and it is not associated with breast size. A woman with large breasts can have non-dense tissue, and a woman with small breasts can have very dense tissue. You can’t tell whether you have dense breasts by looking at or feeling them. Only a mammogram can show that.
Having dense breasts doesn’t automatically mean you’ll develop breast cancer, but it is associated with both a slightly higher risk of breast cancer and reduced sensitivity of mammograms. Some women benefit from additional screening, depending on individual risk factors and medical guidelines. Let’s discuss the types of breast density and the supplemental breast cancer screening options to talk about with a doctor.
Breasts contain three main types of tissue: glandular, fibrous connective, and fatty tissues. Fatty tissue appears dark on a mammogram, while glandular and fibrous connective tissues appear white. The problem is that tumors also appear white, making it difficult to identify what is normal breast tissue and what may be cancer.
Dense breasts have higher amounts of glandular and fibrous connective tissues and lower amounts of fatty tissue. Breast density is classified into four categories using the American College of Radiology BI-RADS system:
Entirely fatty breast tissue: Your breasts are made up of almost all fatty tissue. About 10% of women have this type.
Scattered fibroglandular breast tissue: You have mostly fatty tissue with some dense areas of glandular and fibrous connective tissue. About 40% of women have this type.
Heterogeneously dense breast tissue: You have many areas of glandular and fibrous connective tissue with fewer areas of fatty tissue. About 40% of women have this type.
Extremely dense breast tissue: You have almost entirely glandular and fibrous connective tissue. About 10% of women are in this category and face a slightly higher risk of breast cancer; more research is needed to understand why.
Women in the latter two groups are considered to have “dense breasts.”
If you have entirely fatty or scattered fibroglandular breast tissue, you will see “not dense” on your results. If you have heterogeneously or extremely dense breast tissue, you will see “dense” on your results.
It’s also worth noting that breast density can change over time. It generally decreases as women get older, though the rate varies. The level of density in breast tissue may also be influenced by weight changes, breastfeeding, menopause, and hormone therapy. Breast implants do not affect breast density.
If you have dense breasts, talk with a health care provider about supplemental screening to catch potential breast cancer early.
Mammograms continue to be the gold-standard screening for breast cancer. If you have an average risk of developing breast cancer – meaning you are not at increased risk because of family history, genetics, or other factors – you should get a mammogram each year starting at age 40.
A standard mammogram and 3D mammogram (tomosynthesis) both use a low-dose X-ray to produce an image of the breast. Unfortunately, the sensitivity of a mammogram can go down to as low as 25% to 30% for dense breasts as compared to almost 100% sensitivity for fatty breasts.
Mammograms are still valuable for women with dense breasts. Even with dense breasts, we can still detect ductal carcinoma in situ (DCIS), a very early form of breast cancer, with a mammogram. This is because it is a calcification and not a soft tissue tumor. Because of this, I would never say a mammogram is worthless, despite the density of your breasts.
But to find most invasive cancers among women with dense breasts, we may need to supplement screening with another breast imaging method such as:
Ultrasound: This exam uses sound waves to produce an image of the breast.
Contrast-enhanced mammogram: This exam combines a traditional mammogram with an injection of an iodine-based contrast, which highlights areas of increased blood flow that can indicate the presence of cancer.
Magnetic resonance imaging (MRI): This exam uses powerful magnets and radio waves to create highly detailed images of the breasts.
There are pros and cons to each type of breast screening. A recent study found that contrast-enhanced mammography and MRI can detect three times as many invasive cancers in dense breast tissue as ultrasound. However, contrast-enhanced mammography and MRI are more expensive than an ultrasound. Many insurance plans will not cover them as a screening tool unless your lifetime risk of breast cancer is more than 20%. Ultrasound remains quicker and more widely available, but it detects fewer cancers. 1
If you are allergic to contrast, are claustrophobic, or have an MRI-incompatible device such as some pacemakers or orthopedic hardware, you may not be able to have an MRI. The best next step is to talk with a doctor about your options. Then, check with your insurance company about what it will and will not cover. You also may be eligible for financial assistance through local, state, or federal programs.
If you are called back for additional imaging after a mammogram, try not to be alarmed. Most callbacks are due to areas that need a closer look, and the vast majority turn out to be benign. Still, follow-up testing is important to make sure nothing concerning is missed.
If the screening mammogram is abnormal, the next step is usually a diagnostic mammogram and sometimes an ultrasound to take a focused look at the area. In a smaller number of cases, a biopsy may be recommended, which means taking a tiny tissue sample to check for cancer.
If you are diagnosed with breast cancer, your care team will create a treatment plan tailored to your needs. Advances in breast cancer therapy are improving outcomes every year. At UT Southwestern, my colleagues and I are leading research on nonsurgical treatments for early-stage breast cancer, with the goal of helping more women avoid mastectomies and receive care that is less toxic but equally effective.
Screening remains the highest contributor to breast cancer survival. Don’t put off your annual mammogram – screening helps identify early-stage breast cancer before symptoms begin, when the chances for successful treatment are highest.
My colleagues and I are always looking for ways to improve breast cancer screening, including developing artificial intelligence (AI) models to improve detection. We published a study in spring 2025 that shows patients who responded to a survey have cautious support for AI implementation in screening mammography.
The survey, completed by 518 participants in 2023, found:
71% preferred AI to be used as a second reader of mammograms, after a radiologist.
4.4% were comfortable with AI alone interpreting their mammogram.
88.9% requested a review after an AI-reported abnormal screening vs 51.3% after a radiologist review.
Patients who had a close relative diagnosed with breast cancer were more likely to request additional reviews of any abnormality.
Hispanic and non-Hispanic Black patients reported higher concerns about AI bias in mammograms.
Reference:
1. https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(25)00582-3/fulltext?utm_campaign=tlpr&utm_medium=email&_hsenc=p2ANqtz-8zvDQNSRIyKpl6gifWubmm4uyYehVVebv8W86Myui7aDzYAxGaJTnksAnk5nxE9yU8gWeR8lJ01z8B9H5GnIo3zXDq2A&_hsmi=362180890&utm_content=362180890&utm_source=hs_email
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