Learn more in Pam's recently published book,
101 Things You Should Know About Breast Cancer.
Why is breast density significant?
Dense breasts contain more glandular and connective tissue than do fatty breasts. Every woman has different amounts of the different types of tissue in her breasts. Breast cancer itself is dense. 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 finding cancer in dense breast tissue that "it's like looking for a polar bear in a snowstorm." Breast cancers are readily seen in fatty tissue with up to 98% sensitivity on mammography.

Dense breast tissue itself is also 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.

How do you know if you have dense breasts?
The mammogram is the usual way to know the breast density, though CT and MRI also can show it. You and your doctor cannot tell how dense your breasts are by the way they feel.

Most mammography reports use the following terminology to categorize and describe breast density using four different categories: (A) mostly fatty; (B) scattered fibroglandular tissue; (C) heterogeneously dense; and (D) extremely dense. The BI-RADS classifications (American College of Radiology Breast Imaging Reporting and Data System) are used as a part of a radiologist's mammographic report. Look for the terms "heterogeneously dense", or "extremely dense" in your mammogram report or letter of your mammography results, which would indicate dense breasts.

How often is cancer missed using standard mammography in women with dense breasts?
With mammography, fewer than half of breast cancers present are detected in women with dense breasts. Despite its limitations, mammography is still an important piece of early detection. Please read more below.

Is dense breast tissue normal?
Yes. About 40% of all women undergoing screening mammography have dense breasts. Breasts tend to become less dense as women go through menopause, but some women continue to have dense breast tissue throughout life. Extremely dense or heterogeneously dense tissue is present in over half of women younger than age 50 years and one-third of women age 50 years and older.

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 help allow small changes to be seen. This is difficult if the previous mammograms are 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
•If you have a family history or other risk factors, ask your doctor or your radiologist if you may qualify for supplemental screening with MRI.
• If you do not qualify for MRI, 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 the D-MIST study with nearly 50,000 women participating, digital mammography was more sensitive than film mammography in finding cancers in women with dense breasts. Sensitivity for women with dense breasts was 55% for film and 70% for digital, though these results were in 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 widely available.

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 cancer detection.

How effective is ultrasound?
Mammography alone finds about 5 cancers per 1000 women screened. When ultrasound is performed in women with dense breasts, another 3 cancers per 1000 women screened are seen only by ultrasound.. The cancers seen only with ultrasound are mostly small invasive cancers that have not yet spread to the lymph nodes. For women at high risk for breast cancer who are not able to have MRI, ultrasound improves 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, and the usual examination requires lying still in a tunnel for 30-60 minutes, though a few centers are starting to offer “fast” MRI that takes less than 10 minutes.

Why isn't ultrasound or MRI 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 often used diagnostically to evaluate areas of concern seen on mammography or to check clinically concerning findings. Screening ultrasound looks at the entire breast, but is not routine in many clinics. Most technologists are not trained in whole breast ultrasound screening and when done, it can be a lengthy process. Technologists are mostly trained in diagnostic ultrasound screening, where they are looking at a single area of concern.

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).

What about 3D mammography?
Tomosynthesis, or 3D mammography is yet another tool in the arsenal of a woman with dense breasts. Read
HERE to learn more from .

Tomosynthesis (3D mammography), ultrasound, and MRI have all been proven to increase the detection of cancer beyond that of digital mammography, with more cancers seen using MRI than ultrasound and more with ultrasound than tomosynthesis, though more comparative studies are needed. The cancers seen only with ultrasound are mostly small invasive cancers which have not yet spread to the lymph nodes; MRI also sees some cancers that are still confined within the ducts (ductal carcinoma in situ) which cannot spread beyond the breast. In most centers you must have an identified area of concern before ultrasound would be done; hence the need for SBE, CBE, and RAM (regular, annual mammograms), to identify areas of concern so further imaging can be done (often with ultrasound). MRI is usually only offered to women who meet high-risk criteria. If tomosynthesis is available, it can show areas of distortion (like a tugging at the fabric of the breast) due to breast cancer that might not show up on a standard digital mammogram, but cancers in dense breasts are not always seen on tomosynthesis.

Other Breast Cancer Facts:
• Approximately 211,000 new diagnoses of breast cancer each year
• Approximately 58,000 new diagnoses of non-invasive breast cancer (ductal carcinoma in situ, DCIS) 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

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, Professor of Radiology, Magee-Womens Hospital of UPMC and the University of Pittsburgh School of Medicine, for reviewing the material presented for content and accuracy.

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