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Why is breast density significant?
Dense breasts contain more glandular and connective tissue. Less dense breasts are mainly made up of fat tissue. Every woman has different amounts of the different types of tissue in her breasts. Breast cancer itself is made up of dense tissue. This means that on a mammogram, a tumor is harder to spot in dense tissue than in fatty tissue, because the tumor looks a lot like the tissue around it. An analogy is often used to describe the way dense tissue looks on film, "It's like looking for a polar bear in a snow storm." Breast cancers are readily seen in fatty tissue with up to 98% sensitivity in film mammography.
Dense breast tissue itself is a risk factor for breast cancer, with the risk 4-6 fold higher in women with extremely dense breasts compared to fatty breasts, and breast cancer is more likely to develop in denser areas of the breast. Extremely dense (>75% dense) or heterogeneously dense  (51-75% dense) is present in over half of women younger than age 50 years and one-third of women age 50 years and older.

How often is cancer missed using standard film mammography, in women with dense breasts?
With film mammography, only 30-55% of breast cancers are detected in women with dense breasts. That's why digital mammography is so helpful. But regardless, mammography is still an important piece of early detection. Please read more below.

What is the prevalence of dense breast tissue in women?

According to the American College of Radiology Imaging Network (ACRIN), 40% of all women undergoing screening mammography have dense breasts. Breasts tend to become less dense as women get older, but some women continue to have dense breast tissue throughout life. Over half of women younger than 50 and one-third of women older than 50 have dense breasts.

How do you know if you have dense breasts?
Only a mammogram can tell you for sure. Look for the terms "heterogeneously dense or very dense", or "extremely dense" in your mammogram report, which would indicate dense breasts.
Most mammography reports use the following terminology to categorize and describe breast density: describing four different categories: (1) entirely fat; (2) scattered fibroglandular densities; (3) heterogeneously dense; and (4) extremely dense. The BIRADS classifications (American College of Radiology Breast Imaging Reporting and Data System) are used as a part of a radiologist's mammographic assessment.

I have dense breasts; what do I do differently, if anything?
It depends on what you are doing now, but these are important factors to consider in addition to nationally recommended guidelines:
• Be diligent with recommended monthly self breast exams and yearly mammography and clinical exams.
• DO NOT skip a year with your annual mammogram. Have prior exams sent to your current facility.
This will allow small changes to be seen. This is difficult if the previous year's film is not available.
• Go to a facility which specializes in breast imaging, when possible, to make sure you have experts who spend most of their time in this area.
• Go to a facility with digital mammography, when possible, if you fit the guidelines (see below).
• Make sure you talk to your doctor about following up any suspicious, palpable lump with further imaging.
• See a breast surgeon or surgeon specializing in this area to follow up on suspicious areas, when unsure.
• Trust your intuition
• Ask for whole breast ultrasound screening if it is offered at your facility and they have the equipment and the expertise to do it.

What is important about digital mammography and where can I have it done?
In a recent study with nearly 50,000 women participating, they found that digital mammography was more sensitive than film in finding cancers in women with dense breasts. Sensitivity for women with dense breasts was only 55% for film and 70% for digital, though these are in the most perfect research conditions. Digital mammography allows the radiologist to see images more clearly and to manipulate the image to see it better (brightness, contrast, size, and orientation). Digital mammography is becoming more widely available. Because of it's popularity, you may need to request it specifically at your imaging facility. Still, choosing a facility with specialization in breast imaging is the most important factor.

Did the study say who would benefit most from digital mammography?
Yes. Digital mammography was significantly better in screening women who fit any of these three categories:
• Under age 50 (no matter density)
• Any age with heterogeneously (very dense) or extremely dense breasts
• Pre- or perimenopausal women of any age (defined as having last menstrual period within 12 months of mammogram)

There was no benefit for women who fit ALL the following categories:
• Over age 50
• Don’t have dense breasts
• Not menstruating

How is ultrasound important?
Ultrasound can be used to evaluate masses that are hard to see on a mammogram. Especially for women with dense breasts, ultrasound is helpful in characterizing lumps or other areas of concern. The Avon/ACRIN 6666 Trial showed that when added to a screening mammogram, among women who were at increased risk of breast cancer and had dense breast tissue, ultrasound increased detection.

How effective is it?
Ultrasound has proven to increase the number of cancers detected by 67-100% in studies at single institutions. In addition, smaller invasive cancers have been found with this technology, usually before the cancer has spread to the lymph nodes. For those at high risk for breast cancer who are not recommended for MRI, it may improve detection of breast cancer over mammography alone. MRI is more sensitive and better for those at high risk, but is costly and insurance may not pay for it. Ultrasound is less costly, doesn’t involve radiation, and may be easier for many women to tolerate and obtain. Breast MRI’s involve IV contrast being injected into the veins while lying still for 30-60 minutes.

Why isn't ultrasound screening used instead of mammography?
Mammograms are still important for women with dense breasts because they are good at showing calcifications which are sometimes produced by early breast cancers.
Ultrasound is used to diagnostically evaluate areas of concern, right now.
Screening ultrasound looks at the entire breast the way screening mammography does now, but is not routine in most clinics. Most technologists are not trained in whole breast ultrasound screening and when done, is a lengthy process. Technologists are mostly trained in diagnostic ultrasound screening, where they are looking at a single area of concern.

The use of screening ultrasound in high risk women has been under investigation with the AVON/ACRIN 6666 trial with Dr. Wendie Berg as the Principal Investigator. The first results of the AVON/ACRIN 6666 trial showed that accuracy in women with dense breasts was 78% with digital mammograhy only, and 91% accuracy with mammograpy AND screening ultrasound. Twenty eight percent more cancers were detected than with mammography alone.

With any test, there is a risk of finding something that needs to be biopsied but is not due to cancer. You may want to check whether your insurance covers screening ultrasound.
About a third of U.S. facilities offer screening ultrasound, so it is reasonable to request it, if offered by your breast imaging facility (if they have good equipment and the expertise to do it).

Other Breast Cancer Facts:
• Approximately 211,000 new diagnoses of breast cancer each year
• Approximately 58,00 new diagnoses of non-invasive each year
• 40,000 women will die this year of breast cancer-one every 13 minutes in the U.S.
• Every 2 minutes someone is diagnosed
• Majority of breast cancers occur in women over 50, but women at any age can have breast cancer

The number one risk factor for breast cancer is BEING A WOMAN, the second is GETTING OLDER!

Seventy-five per cent of the time there are no identifiable risk factors when a woman is diagnosed. You can reduce your risk for disease and improve the quality of your life, but there are no guarantees, or fool-proof formulas for preventing disease.

Learn steps to take for early detection of cancer.

A special thanks to Wendie Berg, MD, PhD, FACR, Breast Imaging Consultant and Study Chair for the American College of Radiology Imaging Network (ACRIN) Protocol on Screening Breast Ultrasound, for reviewing the material presented for content and accuracy

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