Are Your Breasts Dense? What's Your Number?

womanDo you know whether or not your breasts are dense? Most women do not. It is important for all women to know their breast density because it impacts your breast cancer risk, as well as how well mammograms can detect breast cancer. The only way to know your breast density is by the results of your mammogram. Ask your radiologist or your doctor.

What’s in the Number

Doctors use The American College of Radiology’s Breast Imaging Reporting and Data System (BI-RADS) scoring method using a 1-4 rating system. This classification system allows radiologists to measure and describe breast density

  • BI-RADS 1 : less than 25% Dense Breast Tissue
  • BI-RADS 2II - 26-50% Dense Breast Tissue
  • BI-RADS 3 – 51- 75% Dense Breast Tissue
  • BI-RADS 4 - More than 75% Dense Breast Tissue

BIRADS Density 3 and 4 is found in women with dense breasts
BIRADS Density 1 and 2 is what women who do not have dense breasts.

At the GW Breast Center, radiologists who interpret your mammograms are dedicated to breast imaging and will let you know your breast density along with the results of your mammogram. Although several states in the nation now require women be told their breast density (including Virginia), currently Maryland and DC do not. At GW, we are committed to letting every women know her breast density because it impacts her risk of breast cancer.

What is breast density? And how does it impact my risk for cancer?

Breast Density is a measure of the amount of breast tissue a woman has. The more tissue, the greater the density and the higher the risk of breast cancer.  However, in women with dense breast tissue, mammograms are not as effective in detecting the cancer. This is because both breast tissue and breast cancer will appear white on a mammogram and the lack of contrast makes identification of the cancer more difficult. 

Digital mammography is the standard to detect early curable breast cancer. Mammography is effective and is probably the most important reason that smaller more curable breast cancers are being detected and that the death rate from breast cancer is decreasing. However, the ability of mammography to detect breast cancer in women with dense breast tissue is limited. 

The issue of breast density is important. Nearly half of all women in the United States have dense breast tissue.  Women with dense breasts  are at a 4-6 times higher risk of developing breast cancer than women who do not.

Although breast density is loosely associated with age, with nearly three-fourths of women in their 30s having dense breast tissue, more than a quarter of women in their 70s also have dense  breast tissue. Regardless of your age, you may have dense breast tissue.

Below is an example of a mammogram from a woman with dense breast tissue and a large breast cancer. The dense tissue appears white, just as the tumor does, causing the breast tissue to mask the cancer. This is why more than one third of breast cancers are missed by mammography in women with dense breasts.


By comparison, below is an example of a breast cancer in a woman with non- dense breast tissue. The white tumor (circle) in the right breast is easily visible against the dark gray and black non-dense tissue.


Dense Breasts and Other Breast Cancer Risk Factors

Breast cancer is one of the most frequently diagnosed cancers among women. The majority of women diagnosed with breast cancer have no known family history or other risk factors.  Only 5-10% of breast cancers are due to a genetic cause. That’s why screening for breast cancer is so important. The most significant risk factors for breast cancer includes being female and age However, increased breast density is a strong independent risk factor for developing breast cancer. The reason it is so important for women to be aware of their breast density is that there are other approaches, in addition to mammography, which can help detect breast cancers which would not be seen with mammography alone such as Automated Breast Ultrasound (ABUS), Breast Specific Gamma Imaging (BSGI) and Magnetic Resonance Imaging (MRI).

Automated Breast Ultrasound System (ABUS)

ABUSAutomated Breast Ultrasound (ABUS) is a new approach to finding up to 30% more cancers in women who have dense breast tissue, even if that is their only additional risk factor. ABUS is used to answer the need of detecting additional cancer in women where mammography alone may be insufficient due to their greater breast density. It uses ultrasound, which is the same technology used to image the fetus in pregnant women, but in a different way. There is no ionizing radiation and ABUS is a quick, painless and effective way to image dense breasts.

With 3D ultrasound volume and U-Systems software, radiologists can look through hundreds of breast tissue image "slices", looking at layers of dense tissue to find breast cancers which may have been missed on a mammogram. This is different than routine ultrasound of the breasts since the images from ABUS allows you to see in projections that routine ultrasound cannot which results in detecting more breast cancers and less false negatives, that is findings due to images which are not cancer.

A complete ABUS exam takes about 15 minutes. Positioned comfortably on the exam table, most patients report the ABUS procedure to be painless; however, some women with very sensitive breast tissue have complained about minor discomfort during the scanning process.

Before starting the exam, the ABUS operator attaches a sheer membrane to the ultrasound scanner. A layer of lotion is then applied to the breast, which ensures good contact between the ultrasound transducer and the skin. To guarantee the best image quality, the sheer stabilizing membrane of the somo•v ABUS is positioned on the breast during scanning, which gently flattens the breast tissue against the body and prevents breast movement.

The operator initiates the scanning process. A 10-second preview scan automatically determines the patient's unique breast tissue signature so the ideal ultrasound imaging parameters can be set by the software. Then, the actual image scan begins and lasts about 60 seconds. The technologist follows the display monitor in real-time to ensure proper breast coverage and tissue contact during the scan. Typically, three scans are performed on each breast for a complete scan of the breast volume.

The 3D ultrasound images are then sent to the somo•VIEWer workstation for physician’s review, either immediately following the exam or at a later point in the patient's care. There the specialized, expert radiologist interprets the ABUS scan along with the women’s mammogram and clinical history. All together, the result is a more accurate way of detecting breast cancer in women with dense breasts.  Even women with prior cancer, breast surgery or implants benefit from the additional information ABUS offers.

Dilon Gamma Camera (BSGI)

The Dilon Gamma Camera is designed to perform Breast-Specific Gamma Imaging/Molecular Breast Imaging (BSGI/MBI), which provides a high-resolution metabolic approach to imaging the breast: that is, BSGI looks at the breast tissue from the perspective of how it functions, and not just how it looks, as mammography and ultrasound do. A BSGI/MBI exam can indentify early breast cancer—as small as 1 mm, especially in difficult-to-diagnose patients. Used in addition to mammography, BSGI allows the physician to see the breast more clearly and may find cancers which would otherwise not be seen as well as may distinguish between benign and malignant tissue.

In comparison to existing gamma camera technology, the Dilon 6800 is able to detect smaller cancers and those in portions of the breast not well imaged with the currently available technology.

Interested in how a BSGI/MBI exam works?

Prior to a BSGI/MBI exam, patients are injected in the arm with a small amount of radiotracer agent that is absorbed by all the cells in the body.  Cancerous cells in the breast absorb a greater amount of the tracing agent than normal, healthy cells; therefore, cancerous cells will, in general, appear as “dark spots” on the BSGI image.

A special camera is then used to identify whether there is evidence of an abnormal area. In this test, the tissue in the breast is evaluated in a physiologic approach (the way the tissue functions) compared to the anatomic approach of mammography and ultrasound (the way the tissue looks). The GW Breast Center has the Dilon 6800, a unique high-resolution nuclear medicine camera, which can be used to detect the earliest breast cancers. This may be most advantageous in women with dense breast or in whom physical examination or mammography is difficult to interpret, such as women who have previously had breast surgery or in women who are at very high risk of breast cancer, such as women with a personal history of breast cancer or those who have multiple members of their family with breast cancer.  Furthermore, BSGI detects an additional area of cancer in 10% of women with a newly diagnosed breast cancer. So if you have recently been diagnosed with breast cancer, BSGI can be very helpful to identify any additional areas of cancer that mammography and ultrasound cannot detect.

Magnetic Resonance Imaging (MRI)

An MRI measures the electromagnetic signals that your body emits by using magnet and radio waves. Signals are then converted into exact images of the body to detect abnormalities including cancer. MRI is used as a problem-solving tool to evaluate either a lump in the breast or something found on a mammogram. MRI is also the optimal imaging technique for evaluating breast implants. The decision to use MRI should be made jointly by you, your physician and the radiologist.

The GW Breast Center has advanced, comfortable MRI technology, including the new Sentinelle Breast MRI table which is designed for the comfort as well as to get the latest, highest resolution images. 

MRI requires an injection of contrast in the arm to allow us to see how the breast is functioning. There is no radioactivity involved in MRI imaging. However, not everyone can have an MRI. Women who have some implantable devices, like pacemakers, cannot have MRI. Also, women with kidney problems or who are obese may not be able to get MRI examinations. For those women, BSGI can be performed.

The GW Breast Center is the only facility in the Mid Atlantic Area with Breast Specific Gamma Imaging and Automatic Whole Breast Ultrasound, demonstrating our commitment to offering women the advanced technology to personalize breast screening and  imaging to the individual women’s breast density and specific needs. 

The GW Breast Center offers a patient-focused environment. Radiologists on the medical staff at the GW Breast Center teach other radiologists throughout the Washington area as well as in the US and throughout the world how to image and interpret breast imaging studies to achieve the optimal outcome.

For additional information, please call 202-741-2288.

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