What Does It Mean to Have Dense Breasts?

A mammogram will reveal your level of breast tissue density. Have you had a mammogram? Do you know your level of density? It is critical for women to know their density level because “Women with dense breasts have a higher risk of getting breast cancer! If you have dense breasts, then a mammogram will NOT find a tumor in the early stages. It’s like trying to spot a golf ball in a snow storm. (see the images below)

What Are the Parts of the Breast?

A woman’s breast has three kinds of tissue

  • Fibrous tissue holds the breast tissue in place.
  • Glandular tissue is the part of the breast that makes milk, called the lobes, and the tubes that carry milk to the nipple, called ducts. Together, fibrous and glandular tissue are called fibroglandular tissue.
  • Fatty tissue fills the space between the fibrous tissue, lobes, and ducts. It gives the breasts their size and shape.

What Is Breast Density?

Breast density reflects the amount of fibrous and glandular tissue in a woman’s breasts compared with the amount of fatty tissue in the breasts, as seen on a mammogram.

On a mammography report, breast density is assigned to one of the following four categories—

  • The breasts are almost entirely fatty (about 10% of women).
  • A few areas of dense tissue are scattered through the breasts (about 40% of women).
  • The breasts are evenly dense throughout (about 40% of women).
  • The breasts are extremely dense (about 10% of women).

Women in the first two categories are said to have low-density, non-dense, or fatty breasts. Women in the second two categories are said to have high-density or dense breasts. Almost half of women who are 40 years old or older have dense breasts.

Why Is Breast Density Important?

The image on the left shows a mostly fatty breast, and the image on the right shows a dense breast.

Breast Cancer Risk

Women with dense breasts have a higher chance of getting breast cancer. The more dense your breasts are, the higher your risk. Scientists don’t know for sure why this is true.

Breast cancer patients who have dense breasts are not more likely to die from breast cancer than patients with non-dense (fatty) breasts.


Dense tissue can hide cancers. Fibrous and glandular tissue looks white on a mammogram. So does a possible tumor. Because it’s hard to tell the difference between a tumor and dense breast tissue on a mammogram, a small tumor may be missed.

Who Is More Likely to Have Dense Breasts?

The density of your breasts can change over time. Generally, you’re more likely to have dense breasts if you—

  • Are younger.
  • Are pregnant or breastfeeding.
  • Are taking hormone replacement therapy.
  • Have a lower body weight.

What Should I Do If I Have Dense Breasts?

Dense breasts are just one of several risk factors for breast cancer. Consult with your health care professional and request other follow-up screening tests if you have a high level of dense breast tissue. 

Different tests are available that can reveal high levels of concern showing a disease in process that can be missed on a mammogram.  Keep in mind that no screening test is 100% and that “False Positive test results can lead to other invasive and unnecessary testing, like a needle biopsy.

Your doctor should suggest one of these other tests if you have dense breast tissue;

  • Breast ultrasound – A screening tool that uses sound waves to make detailed pictures, called sonograms. Safe with NO radiation.
  • Breast thermogram – Medical thermal imaging without radiation, compression, or physical contact.
  • Magnetic resonance imaging (MRI) – A scan that uses a magnet linked to a computer. The MRI scan makes detailed pictures of areas inside the breast, and may also use contrast to determine if a lump is malignant. Always consult with your health care professional about the pros and cons of your options.

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