Breast Density

What is the Dense Breast Notification, Education Act?

The Breast Density Notification and Awareness Bill, approved by the Rhode Island legislation and is effective as of October 1, 2014, requires all mammography providers to inform women of their breast density level as interpreted on their mammogram.

How is breast density defined?

Breasts are made up of a mixture of fibrous and glandular tissue and fatty tissue. Your breasts are considered dense if you have a lot of fibrous or glandular tissue but not much fat. The category of breast density depends on the percentage of breast tissue made up of this denser tissue compared to the fatty tissue.  Density may decrease with age, but there is little, if any, change in most women.

What are the categories of breast density and how many women fall into each group?

Breast density is determined by the radiologist who reads your mammogram. The American College of Radiology defines breast density in the following categories: 

If your breast density is:Number of women with this typeDo I have “dense breast tissue”?
Almost entirely fatty10% of womenNo
Scattered areas of fibro-glandular density40% of womenNo
Heterogeneously dense / dense40% of womenYes
Extremely dense10% of womenYes

The 50% of women with “Heterogeneously” and “Extremely” dense breasts are those that are considered to have “Dense breasts”.

What is the significance of breast density?

Having dense breasts may increase your risk of breast cancer in two ways. First, denser tissue may make it more difficult to detect breast cancer (masking). The chance that disease will be detected decreases as the density of breast tissue increases. Second, having dense breasts is a risk factor for breast cancer.

What is my risk of breast cancer?

The risk that you will be diagnosed with breast cancer during the next ten years of your life depends on your current age:
-Age 30: 0.44% (1 in 227)
-Age 40: 1.47% (1 in 68)
-Age 50: 2.38% (1 in 42)
-Age 60: 3.56% (1 in 28)
-Age 70: 3.82% (1 in 26)

How does breast density change the cancer risk?

Compared to women with average breast density, the risk for the 40% of women with “Heterogeneously dense” breasts is about 1.2 times greater and the risk for the 10% of women with “Extremely dense” breasts is about 2 times greater. Note that a person’s risk also includes other factors such as gene mutations, family history, and personal history.

If I want to have additional tests done, what are my options?

Rhode Island Medical Imaging offers two additional tests:

Screening breast MRI has been shown to increase the rate of cancer detection. However, it may also show more findings that are not cancer, which can result in added testing and unnecessary biopsies. MRI is recommended for screening in patients at very high risk (>20% lifetime risk of breast cancer). Some people recommend MRI for women with intermediate risk (15-20% lifetime risk of breast cancer) and dense breasts. Due to the on-site expertise of women’s imaging, all RIMI breast MRI’s are done at the Randall Square facility in Providence.

In women with dense breasts but no other risk factors, some studies have shown that whole breast ultrasound can detect an additional 1.6 to 4 cancers for every 1000 women screened. However, ultrasound generates many more biopsies than mammogram (up to 300 for every 1000 women screened) and most of these additional biopsies ultimately end up not showing cancer.

What is the cost of supplemental screening tests?

Because there are so many different insurance plans, it is recommended to check with your insurance carrier for your specific coverage.

Do radiologists recommend additional screening in women with dense breasts?

There is currently no formal recommendation from the American College of Radiology regarding additional screening, beyond mammography, based solely on breast density.

If I do not have dense breasts, do I still need a mammogram?

Women without dense breast tissue should still get an annual mammogram.  This breast tissue type is easier to evaluate and mammograms are most effective at detecting breast cancer in women that have mostly fatty breast tissue. Therefore, Rhode Island Medical Imaging recommends annual mammograms for women 40 and older, along with monthly self-breast exams and yearly breast exams by your physician.

Where can I find additional information?

The American College of Radiology 

The American College of Obstetricians and Gynecologists 

The American Cancer Society 

Are You Dense Advocacy 

The California Breast Density Information Group 


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