Breast Density: Why You Should Care

Patient Expert

A storm is brewing in the medical community, as doctors and radiologists argue the pros and cons of informing women whether or not they have dense breasts, as determined by mammogram results.

The pros? Breast density has recently been determined to be the #2 risk factor for breast cancer, second only to age. If a woman has very dense breasts, she's more likely to develop breast cancer than women with less dense breasts; she deserves to know about this risk.

The cons? Women finding out they have dense breasts may be unduly upset. They may demand additional screening tests beyond mammography to try to identify any potential tumors in their early stages - a costly process, and one that's likely to result in needless biopsies, and perhaps even unnecessary treatment.

What do you think?

In the past 5 years, evidence has been accumulating that a woman's breast density - the balance of fibroglandular tissue to fat in her breasts - plays a significant role in cancer risk.

Thankfully, a study published Monday (August 20) in the Journal of the National Cancer Institute affirms that this risk applies only to being diagnosed with breast cancer - not to the risk of dying from it.

Still, women identified as having the densest breasts (i.e., breasts with little fat) are 4 to 6 times more likely to develop breast cancer than women with the lowest breast density. Dense breasts are now more of a breast cancer risk factor than family history.

Dense breasts can't be identified by look, or feel, or by anyone other than a radiologist reading a mammogram. There are specific categories of breast density - four, to be exact - and of those four, only the highest - where fibroglandular tissue represents more than 75% of the breast - puts a woman at increased risk for cancer.

Federal law requires a radiologist reading a woman's mammogram to note in the report to her doctor exactly what category she falls into. The issue is, the vast majority of physicians fail to pass this information along to their patients.

Why? Well, there's another factor at play here. The most commonly used breast cancer screening tool, the mammogram, isn't foolproof, by any means. For women with very dense breasts, a recent study showed that mammograms missed 60% to 75% of the cancers later identified by other screening methods. (Dean, 2012)

To effectively find breast cancer in its earliest stages, women with dense breasts need additional screening: ultrasound, possibly MRI, and perhaps even a new type of screening gradually making its way into the marketplace: molecular breast imaging (MBI).

Throw in another curveball: women's breast density isn't static; it changes with age. While about 66% of premenopausal women have breasts dense enough to challenge a mammogram, that's true for only about 25% of post-menopausal women. And the transition isn't always straight; women may have dense breasts one year, less dense the next, then denser again the following year.

Finally, some medical researchers and statisticians question the long-held belief that early detection of breast cancer saves lives. They say that many breast cancers are actually not life-threatening, and would disappear on their own without treatment. And the ones most likely to kill a woman seem relatively uninfluenced by when they're found: early, or later.

Add it all up, and you have a confusing situation, one bound to become divisive: the medical community and insurers on one side, women worried about their health on the other.

Four states - New York, Connecticut, Texas, and Virginia - currently require that doctors include information about a woman's breast density in her mammogram report. Legislation around release of that information is pending in 12 additional states. So in the near future, an assessment of breast density may very well become a normal part of your yearly mammogram report.

In the meantime, it's your choice whether or not to find out how dense your breasts are. Your doctor knows; do you want to know, too?

If you have dense breasts, what would you do with the information? Would your insurance company pay for additional screening (if you live in Connecticut, at least, the answer is yes). How well would you handle the anxiety of knowing your breast cancer risk is higher than that of other women?

Right now, without knowing your own breast density, those decisions aren't yours to make. If you want to make them - ask your doctor how dense your breasts are.

Read about molecular breast imaging, and a special ultrasound that improves cancer screening in women with dense breasts.

Learn more about breast density.


Beck, M. (2012, August 7). The latest mammogram controversy: density. Retrieved from

Dean, J. (2012, August 7). Are you dense? day encourages women to learn about breast health. Retrieved from