Breast Cancer 101

Breast Density

Breast cancers may be harder to detect in women with dense breasts using mammography alone.

California Breast Density Notification Law

In California, medical centers that perform mammography studies are legally required to inform women, and their physicians, if their mammograms reveal dense breast tissue. Approximately one-half of women have dense breast tissue. They will receive a written report containing the following notice:

Your mammogram shows that your breast tissue is dense. Dense breast tissue is common and is not abnormal. However, dense breast tissue can make it harder to evaluate the results of your mammogram and may also be associated with an increased risk of breast cancer.

While receiving this information may at first be confusing, notification empowers women – helping women to make better-informed decisions.

Women with dense breasts should consider consulting with their physicians to learn about supplemental breast screening in combination with mammography. Breastlink recommends all women, regardless of their breast density, receive an annual mammogram after they reach the age of 40.

What Makes Dense Breasts Different?

Breasts are composed of fibroglandular tissue and fatty tissue. Dense breasts contain more fibroglandular tissue than fatty tissue. Approximately one-half of women have dense breasts.

Women cannot tell that their breasts are dense simply by touching them. Breast density is revealed on a mammogram. Fatty tissue appears as a dark shade of grey on mammograms and fibroglandular tissue appears as a light shade of white. Because many breast abnormalities also appear as shades of white on mammograms, it can be difficult for radiologists to detect breast cancers in women with dense breasts using mammography alone.

Radiologists grade breast density according to a standardized classification system called Breast Imaging Reporting and Data System, which provides four levels of breast density:

  • Fatty
  • Scattered fibroglandular
  • Heterogeneously dense
  • Extremely dense.

Are Dense Breasts a Breast Cancer Risk Factor?

Some recent research studies suggest having dense breasts raises a woman’s risk for developing breast cancer. Other research suggests that cancers can be harder to detect in women with dense breasts using mammography alone.

  • Women with heterogeneously dense or extremely dense breasts were more than three times as likely to develop breast cancer than women with fatty breasts or scattered fibroglandular densities, according to a study published August 2011 in Journal of the National Cancer Institute.
  • Women with fibroglandular tissue composing more than 75 percent of their breasts were nearly five times as like to develop breast cancer than women with fibroglandular tissue composing 10 percent or less of their breasts, according to a study published January 2007 in The New England Journal of Medicine.

Despite evidence such as this, the medical community has not conclusively agreed that having dense breasts increases a woman’s risk for breast cancer.

BI-RADS Breast Density Classification System

The Breast Imaging Reporting and Data System (BI-RADS) is a standardized classification system that radiologists use to report breast density findings. They grade breast density on a scale of 1 to 4. Here is what those grades mean:

  1. Breast tissue is almost entirely fat with less than 25 percent of the breast composed of glandular tissue.
  2. Breast tissue contains scattered fibroglandular densities with between 25 and 50 percent of the breast composed of glandular tissue.
  3. Breast tissue is heterogeneously dense with between 51 and 75 percent of the breast composed of glandular tissue.
  4. Breast tissue is extremely dense with more than 75 percent of the breast composed of glandular tissue.

Breast Cancer Risk Assessment at Breastlink

At Breastlink, we believe knowledge is power. We want to help you better understand your personal risk for developing breast cancer, so that you can make the best lifestyle choices and health care decisions to promote your breast health.

Our comprehensive risk assessment program is designed to provide you knowledge of your personal risk factors and is covered by most insurance plans. Visit our Risk Assessment Program.



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