Breast Density: What Women Need to Know

Breast density refers to the amount of fibroglandular tissue present in a woman’s breasts. Dense breasts contain more fibroglandular tissue than fatty tissue, and they can make it more difficult for radiologists to detect breast cancers using mammography alone. In addition, recent research suggests that having dense breasts can increase a woman’s risk for developing breast cancer.

California Breast Density Notification Law

The California Breast Density Notification Law requires medical centers that perform mammography studies to inform women and their physicians if their mammograms reveal dense breast tissue. Approximately one-half of women have dense breast tissue. Women who receive this information may at first find it confusing, but it can help them make better-informed decisions about their breast health.

The written report that women with dense breast tissue receive will contain 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.

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

Understanding Breast Density

Women cannot determine if their breasts are dense by touching them. Breast density is revealed on a mammogram. Fatty tissue appears as a dark shade of grey on mammograms, while fibroglandular tissue appears as a light shade of white. Radiologists grade breast density according to the standardized classification system called the Breast Imaging Reporting and Data System (BI-RADS), which provides four levels of breast density:

• Fatty
• Scattered fibroglandular
• Heterogeneously dense
• Extremely dense

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:

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

Are Dense Breasts a Breast Cancer Risk Factor?

Some recent research studies suggest that 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. For example, 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 in the Journal of the National Cancer Institute in August 2011. Another study published in The New England Journal of Medicine in January 2007 found that women with fibroglandular tissue composing more than 75% of their breasts were nearly five times as likely to develop breast cancer than women with fibroglandular tissue composing 10% or less of their breasts.

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

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.