Dense Breast Tissue

Breast density is an indicator of glandular tissue relative to fatty tissue in your breasts. All breasts have a mix of these different types of tissues, but the balance can differ.

Radiologists use the Breast Imaging Reporting and Data System (BI-RAD) to measure fibroglandular density. This data system puts breast tissue into four categories, ranging from mostly fatty to mostly dense tissue. Categories C and D qualify as dense. Most people are in the middle (Categories B and C).

The four categories of breast density are:

• Category A (Almost entirely fatty): Mostly fatty tissue
• Category B (Scattered fibroglandular density): A mix of dense and fatty tissue, but mostly fatty
• Category C (Heterogeneously dense): A mix of dense and fatty tissue, but mostly dense
• Category D (Extremely dense): Almost all dense breast tissue

If your mammogram reading shows extremely dense tissue, then you have dense breasts. About half of the females in the general population have dense breast tissue.

How does having dense breast tissue affect me?

Dense breast tissue is normal. It’s not a disease. But it’s a known risk factor for breast cancer. Denser tissue looks brighter in images — like tumors do — while fatty tissue looks darker. This means small tumors can hide in dense breast tissue.

Dense breast tissue also means that you have a little more of the type of tissue that breast cancer grows in. Most breast cancer starts in your glandular tissue. Some types can also start in your fibrous connective tissue. These two factors give you a slightly higher overall risk of developing breast cancer.

What causes dense breast tissue?

In general, your breast density is written in your genes. You get it from your biological parents. But there are a few things that can affect your breast density to some degree during your lifetime.

Risk factors

Risk factors include:

• Age: Dense breast tissue is more common in younger women and tends to decrease with age.
• Hormones: Conditions that raise your estrogen levels can increase your breast density, including pregnancy and breastfeeding. Taking hormone replacement therapy can also increase it.
• Body weight: People with a low body mass index (BMI) are more likely to have denser breast tissue. Gaining a lot of weight can add more fatty tissue to your breasts. But it won’t reduce the dense breast tissue you have. And it won’t lower your overall cancer risk.

How do you know if you have dense breast tissue?

Dense breast tissue doesn’t cause any symptoms. It doesn’t affect what your breasts look like or feel like. You won’t be able to tell that you have it by doing a breast self-exam or by getting a physical exam. Only medical imaging tests can detect it. Most people find out when they have their first mammogram.

How doctors diagnose dense breast tissue

Doctors don’t specifically test for dense breast tissue. But when you have a mammogram, your radiologist will notice it. In the U.S., the FDA requires your mammogram report to state if your breast tissue is “dense” or “not dense.” This is because it can affect your results, as well as cancer risk.

Is there a treatment for dense breast tissue?

There’s no treatment to reduce your dense breast tissue. But if you have dense breast tissue, your healthcare provider might suggest doing a personalized breast cancer risk assessment. Based on the results, they might recommend supplemental or additional breast cancer screenings after a normal screening mammogram.

These might include:

• 3D mammogram (digital breast tomosynthesis): This advanced type of mammogram is more accurate for examining dense breast tissue. Look for mammogram centers that offer it.
• Whole breast ultrasound: Ultrasound is a noninvasive, supplemental screening test used for those with dense breasts. It’s quick, easy and affordable.
• Breast MRI: For this test, a healthcare provider injects a contrast dye into your vein before scanning you. The dye travels to your breasts and becomes concentrated in any tumors there. Breast MRI is the most sensitive tool for detecting invasive breast cancer.
• Molecular breast imaging (MBI): This test uses special scanning equipment and a radioactive tracer that goes in your vein. The tracer makes cancer cells light up while others appear darker.

Lifestyle changes to reduce breast cancer risk

In addition to more screenings, your provider might recommend adjusting certain health and lifestyle factors that affect your overall cancer risk. Unlike your breast tissue density, these are things that you might be able to change. For example, you can significantly reduce your breast cancer risk by:

• Maintaining a healthy weight for you: Overall, having overweight or obesity raises your cancer risk — even if you have dense breast tissue. Adding fat tissue won’t change the odds in your favor.
• Getting regular physical activity: Regular exercise lowers your breast cancer risk by an average of 25%. If you do get cancer, exercise lowers the risk of it coming back after treatment (recurrence).
• Avoiding toxic substances: Reducing or eliminating alcohol and tobacco can reduce your risk of all cancers. You should also consider other carcinogens that might lurk in your environment.

Should I worry about dense breast tissue?

Many factors affect your breast cancer risk — breast density is just one of them. If you’re like most people and only have moderately dense breast tissue (“heterogeneously dense”), this isn’t a major risk factor by itself. Having extremely dense breast tissue is a greater risk factor — but it’s still only one.

How you feel about your risk is personal and valid. But worrying can’t help. Whether your risk is statistically high, or just too high for your comfort, talk to your healthcare provider about practical ways to reduce it. Taking their advice can bring you closer to an average risk level, despite dense breast tissue.