Topic Overview

What are dense breasts?

Breasts come in all shapes and sizes. The tissue inside your breasts can be different types too. Some breast tissue is fatty. Other breast tissue is dense. "Dense" means it's made of thick, fibrous tissue and milk glands.

There are four levels of breast density:

  • Level 1: Almost all fatty tissue (1 out of 10 women)
  • Level 2: Scattered areas of dense tissue, but mostly fatty tissue (4 out of 10 women)
  • Level 3: Mixed dense and fatty tissue, also called heterogeneous (4 out of 10 women)
  • Level 4: Extremely dense tissue (1 out of 10 women)

All of these breast types are normal. Level 3 and level 4 are dense breasts.

Things that can affect your breast density include your family history (genetics), being pregnant, and using estrogen hormone therapy. Your age can also make a difference. Breast tissue in younger women tends to be denser than in older women who have been through menopause.

Why is it important to know about your breast density?

On its own, breast density is not a major risk factor for cancer. Your level of breast density is one piece of your total cancer risk. Your overall risk is based on facts like how old you are, whether you've ever had breast cancer before, and whether any of your close relatives, such as your mother or sister, have had breast cancer.

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.

How do you learn about your breast density?

You can't tell how dense your breasts are by looking in the mirror or feeling them. A mammogram is the only way to tell how dense your breasts are.

When you have a mammogram, a radiologist will read your mammogram and send a report to your doctor. In some areas, breast density may not be included with your mammogram report. When you have a mammogram, you may be able to request that your breast density results be included with your mammogram report.

If you have questions about your breast density or other concerns, talk to your doctor.

What are my options for screening dense breasts for breast cancer?

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

Talk with your doctor about your breast density and any other breast cancer risk factors you have. Based on your unique information, your doctor can help you decide about screening.

Screening options vary from province to province. Your screening options may include:

  • Mammogram only. A mammogram is 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 it often can't tell you what is cancer and what isn't. Most "abnormal" spots on MRI turn out to be harmless, especially in women with a low risk for breast cancer.

If breast cancer screening tests can't tell you that a spot is harmless, your next step is to decide whether to have a biopsy tested for cancer cells.

Newer screening technology

There are new tests for detecting breast cancer. But they need more research before they become widely available. The most promising of these is digital breast tomosynthesis. This test is also called tomography or 3D mammography.


ByHealthwise Staff
Primary Medical Reviewer Sarah Marshall, MD - Family Medicine
Kathleen Romito, MD - Family Medicine
Femi Olatunbosun, MB, FRCSC - Obstetrics and Gynecology
Specialist Medical Reviewer Howard Schaff, MD - Diagnostic Radiology

Current as ofNovember 20, 2015