Breast Cancer Screening and Dense Breasts: What Are My Options?

Dense breast tissue is made up of thick fibrous tissue and milk glands.

Most women have breasts with a mix of dense tissue and fatty tissue. Some women have very dense or very fatty breasts. All of these breast types are normal.

There are four levels of breast density:

• Almost all fatty tissue (1 out of 10 women)
• Scattered areas of dense tissue, but mostly fatty tissue (4 out of 10 women)
• Mixed dense and fatty tissue, also called heterogeneous (4 out of 10 women)
• Extremely dense tissue (1 out of 10 women)

You can't tell how dense your breasts are by looking in the mirror or feeling them. The mammogram report sent to your doctor tells how dense your breasts are. It's written by the radiologist who reads your mammogram.

Having dense breasts may affect your plans for breast cancer screening. The more dense a breast is, the harder it is to see cancer on a mammogram image. That's because dense tissue looks white onscreen, just like cancer does.

Breast cancer tends to grow in dense breast tissue more often than in fatty breast tissue. So having dense breasts may slightly increase your risk for breast cancer.

Having dense breasts may slightly increase your risk for breast cancer. But your risk for breast cancer depends on many things.

Sometimes women think that their breast cancer risk is higher than it really is. If you don't know how high your risk actually is, talk to your doctor to find out.

If there's a high risk of breast cancer in your family, talk to your doctor about getting genetic testing and genetic counseling.

To learn more about your risk level, go to www.cancer.gov/bcrisktool.

There are several breast cancer screening tests. Each type of test shows breast tissue differently and finds things that the others don't.

• Mammogram only. Mammograms are recommended for all women who need breast cancer screening. A mammogram is the only test that can show tiny bits of calcium that can be a sign of cancer, even in dense breast tissue.
• Mammogram and breast ultrasound. These tests work well together for screening dense breast tissue. An ultrasound can show if a lump seen on a mammogram is a harmless fluid-filled cyst or something solid that could be a problem.
• Mammogram and MRI. MRI shows clear detail of breast tissue, but often can't tell you what is cancer and what isn't. Many "abnormal" spots on MRI turn out to not be cancer, especially in women with a low risk for breast cancer.

Digital breast tomosynthesis, sometimes called DBT or 3-D mammogram, is a test that uses new technology. It may be used alone or with a digital mammogram. DBT seems to work better than mammogram alone to find cancer in dense breast tissue. But it is still being studied to see how well it works.

No screening test is perfect. Each carries the risk of doing too little or too much.

• The risk of less testing is missing a cancer that needs treatment (called a false-negative result). With dense breast tissue, missing a cancer is most likely with a mammogram-only screening.
• The risk of more testing is:
  • Finding something that looks like a cancer when it's not (called a false-positive result). This can lead to unneeded tests or biopsy. False-positives are more common with MRI screening, since it shows the most detail.
  • Finding cancer that would never cause a problem, such as a cancer that grows so slowly that even without treatment it would never affect a woman's health. But since there is no way to know which breast cancers will cause harm, any cancer is usually treated.

Different breast imaging tests can detect cancer in different ways. No single test can find every cancer.

• The benefit of getting less testing (a mammogram-only screening) is that it raises your chances of finding cancer without the added risks of more testing.
• The benefit of getting more testing (a mammogram plus another screening test) is that you may further raise your chances of finding cancer. But having more testing means that your chances for a false-positive result are higher. You may end up having tests that you don't need, such as a biopsy.

If you have dense breasts but no other risk factors for breast cancer, a mammogram is the recommended test. There isn't enough evidence from studies to show that having other tests will help you.^{footnote 1}

If you have dense breasts and other risk factors for breast cancer, talk with your doctor to decide about screening. In some cases, if further screening is needed, a breast ultrasound or MRI may be done.

Team up with your doctor to decide what makes the most sense for you.