Breast Density and Why It Matters

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When your doctor orders a more advanced form of mammography because you have “dense” breasts, should you be concerned?

For what you need to know, we chatted with Anne C. Kushwaha, M.D., a diagnostic radiologist at Memorial Hermann Upper Kirby Breast Center, Memorial Hermann Southwest Memorial Breast Center and Memorial Hermann Bobetta Lindig Memorial City Breast Center. Dr. Kushwaha is also a diagnostic radiology professor at The University of Texas MD Anderson Cancer Center.

Q: What is breast density?

A: Breasts are composed of fibrous, glandular and fatty tissues. Your breasts are considered dense if you have little fat but some-to-lots of fibro-glandular tissue.

Q: How do I know if I have dense breasts?

A: Radiologists look at mammograms to rank density visually in four categories: almost entirely fatty (category 1), scattered areas of fibro-glandular tissue (category 2), heterogeneously dense (category 3) and extremely dense (category 4). Only 10 percent of women have either almost entirely fatty breasts or extremely dense breasts. The remaining 80 percent have scattered or heterogeneously (uniformly) dense breasts.

Q: What role does breast density play in the detection of breast cancer?

A: Fat appears dark on mammograms, while fibro-glandular tissues and cancers appear white. “It’s hard to see white on white, and masses may be obscured because there’s less contrast for radiologists to spot them,” Dr. Kushwaha says. This is called “masking” meaning some cancers may be hidden by the overlying tissue and not detectable to the radiologist.

Q: Am I more likely to get cancer if I have dense breasts?

A: “Dense breasts double cancer risk compared to the average risk.”

This is similar to the risk a woman has with a family history of breast cancer.   “No one knows exactly why and it is a topic of current study,” Dr. Kushwaha says.

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Q: Who is most likely to have denser breasts, and does age matter?

A:  It is related to genetics, menopausal status, body mass index, parity (the numbers of pregnancies a woman has had) and sometimes drugs.  Women who have more fat elsewhere in their body often have more fat in their breasts, but not always, Dr. Kushwaha says. “Your density is like a fingerprint. Everyone’s breast tissue pattern is unique. It’s just the way you’re made.”

Q: If I have dense breasts, do I still need mammograms?

A: Yes. Though cancer may be more difficult to spot on traditional mammograms exams are still the only proven examination to lower mortality in women. “They show early signs of cancer, calcifications, which are calcium deposits that appear as white specks on a mammogram but can’t be felt during a manual breast exam,” Dr. Kushwaha says. Ultrasound cannot see calcifications. Radiologists can still detect cancers in a dense breast on mammograms.

Q. Are all mammograms the same?

A:  The latest technology, three-dimensional (3-D) mammography (tomosynthesis) can be performed at the same time as traditional mammograms to boost their accuracy. Much like computed tomography (CT), this newer mammography technique creates 1-millimeter slices of the breast from different angles. “Not only can we find cancers that might not be found on 2-D imaging,” Dr. Kushwaha says, “but 3-D tomosynthesis has been shown to decrease the number of women who are called back for more tests due to false positives.”

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All Memorial Hermann breast centers use digital mammography, in which images are stored electronically, versus film, as in years past. Digital images can be magnified and manipulated and are easier to store, retrieve and share among doctors.

Q: Who should get 3-D mammography with tomosynthesis?

A: Women with any breast density beyond fatty tissue (categories 2-4) should get 3-D mammography with tomosynthesis,” Dr. Kushwaha says.  This is 90 percent of women.

Q: Does 3-D mammography put me at excess radiation risk?

A: Even with the extra mammographic view, “the amount of radiation is still extremely low, less than you get from flying from New York to Los Angeles,” Dr. Kushwaha says.

The American College of Radiology (ACR) endorses breast tomosynthesis, saying recently, “Better sensitivity will likely translate into more lives saved.”

Q: If I have dense breasts, do I need more than a mammogram?

A:“Women with heterogeneously dense or extremely dense breasts can request an ultrasound for additional screening, as it has been shown to increase the amount of cancers detected,” adds Dr. Kushwaha. “For a woman with a lifetime risk of breast cancer over 20 percent, an annual MRI is recommended in addition to mammography.”

Both screening ultrasound and screening MRIs also have been shown to boost the number of benign biopsies that a patient receives. The risks and benefits of additional screening tests should be discussed with your doctor.

 

Q: Does breast density affect my frequency of mammograms?

A: Regardless of your breast density, you should start yearly mammograms at age 40 (unless your doctor suggests you start earlier due to very high family breast cancer risk or presence of a known mutation in either the BRCA1 or BRCA2 gene).

As for when you should cease mammograms, “There is no consensus,” says Dr. Kushwaha. Most recommend continuing screening mammograms as long as you are healthy.

To learn more about breast cancer screening, visit Memorial Hermann Breast Care Centers.

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Tashika Varma