As of January 1, 2019, Washington state law requires that patients be notified if they have dense breasts as determined by mammography.  This information is being provided to increase your awareness of breast density so that you can make better health care decisions.  However, we also recognize that this information may be confusing.  The following information is provided to help you understand breast density and how it can affect you.  It is not meant to replace direct conversation with your health care provider about density and breast cancer risk.

What is Breast Density?

Breasts are made up of a mixture of fatty tissue and fibroglandular tissue.  Breast density refers to the amount of normal, non-fatty tissue visible in a woman's breasts on mammograms.  There are four categories of breast density, ranging from almost all fatty tissue to extremely dense tissue with very little fat.  If your breasts are in the higher two categories (heterogeneously or extremely) they are considered "dense."  It is important to understand that there is no "normal" amount of breast density.  In fact, roughly half of women who undergo screening mammography have dense breasts.

Breast Density in the U.S.
  • 10% of women have almost entirely fatty breasts
  • 10% have extremely dense breasts
  • 80% are classified into one of two middle categories


If Having Dense Breasts is Normal, Why is it Important?

There are two main reasons breast density is important: Density can affect mammograms and breast cancer risk.

Effect on Mammograms

Although mammograms are still useful and accurate for women with dense breasts, cancers can be harder to see in women with dense breasts.  On mammograms, breast masses and tumors look white.  Breast density is also white, and the greater the amount of density, the increased chance that cancer will not be visible on a mammogram.

Breast cancer risk

Density has also been linked to an increase in the odds a woman will develop breast cancer in their lifetime.  Although on average women with dense breasts are a higher risk of developing breast cancer, it is important to note that density is only one of many factors linked to a slight increase in breast cancer risk.


I Have Dense Breasts.  What Should I Do Next?

  • Talk with your provider to see if there is anything besides breast density that may increase your risk of getting breast cancer.  Research studies have not yet shown a clear benefit from additional tests such as ultrasound or MRI for women who have dense breasts without other breast cancer risk factors.
  • You should continue to get yearly mammograms, particularly ones with 3D mammography technology.


What if I Don't Have Dense Breasts?

  • If your breasts are not dense, other factors may still place you at increased risk for breast cancer - including family history of the disease, previous chest radiation treatment for cancer and previous breast biopsies that show you are high risk.  Talk to your doctor and discuss your history.
  • Even if you are at low risk, and have entirely fatty breasts, you should still get an annual mammogram starting at age 40.


Breast Density FAQS

If you have further questions, our FAQs below are a good place to start.


Q: What exactly is dense breast tissue?

A: The breasts are basically made of two types of tissue - fatty tissue and fibroglandular tissue.  These two types of tissue are mixed in varying degrees throughout the breasts.  Women with dense breast tissue have a higher percentage of fibroglandular tissue and women with fatty breast tissue have a higher percentage of fatty tissue.  There is not one "normal" amount of dense or fatty tissue for a woman.

Q: Why do I have dense breast tissue, and can I change this?

A: You are just "built" this way, and your breast density will probably slowly decrease with time.  Some medications, such as hormone replacement therapy, could increase your breast density.  If you are on or considering using hormone replacement therapy, it is a good idea to discuss the risks and benefits of its use with your health care provider.

Q: Does having dense breasts mean I will probably get breast cancer?

A: No! But, having dense breast tissue can increase your risk for breast cancer slightly.  There are many things that can increase your risk of breast cancer, and breast density is just one of them.  Half of the women screened have dense breast tissue, but the great majority of women will not develop breast cancer.  In fact, most women with dense breasts are not at high risk for developing breast cancer.  If you have concerns about your risk, you should discuss this with your health care provider.

Q: If my mammogram is difficult to read because of dense breasts, why should I get one?

A: Mammograms are not perfect, but they have been proven time and time again to save lives, even in women with dense breasts.  Fortunately, Vancouver Radiology offers 3D mammography (also known as tomosynthesis), which can help make a mammogram easier to read and can help find cancers that might otherwise be hidden in dense breasts on regular 2D mammograms.


For more information on breast density, please visit the following sites: