What You Need To Know About Breast Density

Breast density is gaining notoriety as a hotly debated issue in the medical community. What is it all about and what do you need to know in order to be informed?

The Tissue Issue

All breasts are made up of fatty tissue as well as breast, glandular, and connective tissue. The ratio of fatty tissue to the other tissues, however, varies from woman to woman, and breast to breast, and changes over time. Breasts with relatively more glandular and connective (“fibrous”) tissue than fatty tissue, are classified as “dense breasts.” Even the most thorough self-exam cannot determine if a woman has dense breasts – doctors determine where breasts fall on this spectrum by looking at a mammogram.

What’s bad about having dense breasts? A mammogram is an x-ray of the breast, and denser breast tissue can make it more difficult to identify potential tumors. Glandular tissue appears white on mammograms, as does breast cancer. Fatty tissue appears dark gray, making tumors stand out more easily as white spots on scans. In dense breasts, mammograms will miss more than half of cancers present.

Radiologists assign breasts to four categories, and patients who are notified of their breast density are told using these specific terms (so pay attention!):

  • A = Almost entirely fatty
  • B = Scattered areas of fibroglandular density
  • C = Heterogeneously dense
  • D = Extremely dense

Breasts categorized as C or D are considered “dense.” More than half of women younger than fifty have dense breasts, while after menopause, breasts tend to lose density.

“Knowing you have dense breasts is just one step of assessing breast cancer risk.”

So You Have Dense Breasts

Scanning of a breast of the adult woman

Knowing you have dense breasts is just one step of assessing breast cancer risk. According to the American Cancer Society, although having dense breast tissue increases a woman’s risk of developing breast cancer, there are other important risk factors to consider before seeking supplemental screening in addition to mammograms.

Women who have a strong family history of breast cancer, or who have undergone genetic testing and have a disease-causing variation in a breast cancer gene (e.g., BRCA1 or BRCA2) should consider getting an MRI along with their mammograms, as they are considered high risk. Age is the most important risk factor, as risk of developing breast cancer increases as women get older, and risks need to be assessed each year. For women with dense breasts who have moderate to low risk, ultrasound is an option.

While MRI and ultrasound are able to pick up cancers missed in a mammogram, all imaging tests (including mammography) can also reveal suspicious areas that are benign, which may require additional imaging and biopsy, known as “false positives.” In addition, MRI and ultrasound screening are not always fully covered by insurance.

One Woman, Both Doctor and Patient

Lois-Wendie-crop-9-23-15Dr. Wendie Berg, Professor of Radiology at the University of Pittsburgh School of Medicine, had dense breast tissue on her routine 2D and 3D mammogram, but nothing else was noted. “My mother has breast cancer, and was diagnosed when I was in high school,” said Dr. Berg, who also has an aunt who died from metastatic breast cancer. “My mother has dense breasts, and her cancer didn’t show up on a mammogram. She had metastatic nodes and required chemotherapy, so I personally have been aware of the dense breast issue for a long time, over forty years.”

Dr. Berg explained her own revelation with breast cancer: “I was writing a chapter of my breast imaging book on Risk Models, and used my family history to calculate my risk. While my risk had been only moderate the last time I had done this, I found I now had a 19.7% lifetime risk of breast cancer and 20% is the threshold for getting an MRI, according to the American Cancer Society. So I got the MRI and saw for myself, it was obvious that I had breast cancer.”

Dr. Berg’s decision to pursue additional screening methods based on calculating her personal risk and dense breasts, led to an early diagnosis and subsequent lumpectomy enabling her to skip chemotherapy.

“I’m so much better off,” said Dr. Berg. “It’s not ambiguous to me that finding my invasive cancer early mattered.” For her, being proactive in educating herself and being a strong self-advocate when it came to monitoring her dense breasts was worth it.

“Most women don’t have the information they would need to make the choices I made, to advocate for themselves to get what they need,” said Dr. Berg. “And that experience empowered me to act beyond my own patient care and practice to work with advocate JoAnn Pushkin and technologist Cindy Henke-Sarmento to help create a website, Dense Breast-info. The website provides the needed tools to women and their healthcare providers to make informed decisions about screening based on personal risk factors and to understand the benefits and the risks to any testing.”

“The bottom line is that each woman should consult her doctor about her breast type, assess her risk and know her options to ensure she’s receiving optimal care.”

The Larger Discussion

There is growing interest around ensuring doctors inform women of their breast density, however the issue has also entered the political realm. Currently, breast density notification laws have been put into effect in 24 states, which means that, for more than 2 in 3 women in the United States, patients must be supplied some information about their breast density.

Advocacy groups such as Are You Dense? focus on increasing national awareness of breast density and the risks and screening challenges associated with dense breasts. However, not everyone sees the benefits of telling women they have dense breasts, nor do women always know what the notification means.

“I think historically, among [doctors resisting notification laws], the concerns were two fold,” said Dr. Berg. “One was that it might discourage women with dense breasts from getting mammograms. It’s very important to point out that even in dense breasts we do find cancers on mammography. The other piece has been lack of clarity about what to do with density information.”

Nurse talking to mother and daughter

Some doctors argue that knowledge of breast density can cause women to get unnecessary and expensive tests, in addition to causing psychological harm. Other doctors are not well informed around identifying patient risk factors and knowing how to follow-up with patients who have dense breasts. And still others prioritize the prevention of psychological harm of a false positive over the more lasting damage of a late stage diagnosis.

While there is temporary anxiety from a false positive (which may involve additional mammography views, ultrasound, or needle biopsy), there can be permanent anxiety and stress, as well as physical harm, from having cancer detected at a later stage because extra screening was not performed. “Women should be aware that there’s about a 10% chance of recall for extra testing anytime they get a screening, but that should not be equated with the benefit of saving a life or avoiding chemotherapy with early detection of cancer,” said Dr. Berg.

Where Does That Leave You?

The issue of dense breasts is complicated, resulting in the medical community sending at times conflicting messages, but Dr. Berg hopes this conversation will continue to grow and improve.

“The biggest issue is consistency in communication with patients,” Dr. Berg added. “Providing data-driven information is my goal. Part of that is discussion of risks and identifying who should have the screening MRI, and the other part is having ultrasound more available and training enough qualified people to do it.”

The bottom line is that each woman should consult her doctor about her breast type, assess her risk and know her options to ensure she’s receiving optimal care.