So What Are Dense Breasts?

There has been recent discussion around a new law that has been passed in certain states (Conneticut, New York, California, Texas and Virginia) requiring imaging centers that perform mammograms to inform their patient’s if they have dense breast tissue on mammograms. The reason for this is that breast cancers can be covered up in dense breasts.

A recent New York Times article tells how Nancy M. Cappello of Woodbury, Conn. took her story to state legislators when a cancer was discovered on her mammogram. She claims that she was not told she had dense breasts until the cancer was detected. She wanted legislation that would require women be told if they have dense breasts and require that insurance companies cover ultrasound scans for those women. This legislation has raised concern amongst medical professionals since they know that telling women they have dense breasts may lead to false positive findings and unnecessary testing. This could lead to an increased demand on a health care system that is already under strain, not to mention that many physicians are not comfortable with the idea of laws controlling what information is given to patients.

What is important to understand and realize as a patient is that all tests have their limitations and need to be interpreted based on an individuals history and risk factors. Not one test is one hundred percent accurate.

So what are “dense breasts”? In the world of imaging this refers to the amount of white tissue seen on a mammogram. Up to 40% of women can have dense breasts or a lot of white tissue on their mammogram. Age also is a determining factor. Fifty percent of women younger than 50 and a third older than 50 are estimated to have dense breasts.

The dense white tissue may obscure a cancer because cancers also show up as being white on mammograms. Fatty breasts look dark on mammograms and the cancer will stand out as a white mass or irregular white tissue with calcifications which are also white.

Dr. Gretchen Gierach, who reported the results in the Journal of the National Cancer Institute states that women with dense breasts are at higher risk for cancer. No one knows for sure why, but the theory is that there are more ducts and glands where the cancers can form. Tumors might be discovered later in extremely dense breasts, but once diagnosed they weren’t more aggressive or more difficult to treat, stated co-author Dr. Karla Kerlikowske of the University of California, San Francisco, who has studied breast density for a long time.

Dr. Carol H. Lee a radiologist at Sloan-Kettering Cancer Center in New York states that it is not clear if the increased risk is equal for every woman.
So what is done next to look for a possible cancer if the mammogram is negative?
Breast ultrasound is another imaging modality that can be used to look for breast cancer in women with dense breasts or palpable lumps.

The April 2012 issue of JAMA and June 2012 issue of Radiology found that for every 1,000 women screened, adding ultrasound, found 3-5 additional cancers that were not detected on mammograms. It should be noted that in one study it required 63 biopisies or other tests to find the 3 tumours.

MRI is another imaging procedure used to investigate women at high risk with dense breasts.
This is a much more costly investigation and studies are currently under way to determine its role in women at high risk for breast cancer.

So what is a woman to do? Consult your physician to determine your risk category. It’s one more factor to consider along with whether your mother or sister had breast cancer, if you’ve had previous biopsies, and your reproductive history. Learn how to do self breast exams, go for screening mammograms and then with your physician decide if you need additional testing to rule out breast cancer.

To help women become better informed around this topic, the American College of Radiology has provided a brochure for mammography centers to distribute: .