Mammograms are x-rays that help identify cancers of the breast before they are able to be felt.
Mammography looks for a “dense cancer” in the background of the breast tissue. Breast tissue is made of fatty and glandular tissue. The ratio of glandular tissue to fatty tissue is the breast’s “density” and is somewhat related to one’s size, shape and menopausal status, and can be hereditary. Mammographic density is not associated with how “lumpy” or dense the breast feels.
Naturally, the denser the tissue is, the harder it will be to find a cancer that is identified due to its own “density.”
“I often say it is like trying to see the sun in a cloudy sky, with the sun representing a cancer, and the clouds the density of a breast,” says Jennifer Gass, MD, of The Breast Health Centers at Women & Infants and Kent hospitals.
Breast density is a twofold issue for women. It makes it harder to read a mammogram and it has been associated with a modest increase in one’s risk for breast cancer. Why mammographic density causes an increased risk for breast cancer is an area of active research.
In the last several years, many states have enacted legislation that mandates women be informed of their breast density so they can make decisions about additional breast imaging. Three options are available at most institutions to examine dense breasts:
- 3D tomosynthesis, which is a layered breast imaging tool associated with a reduced call-back rate for false positives and earlier detection of cancer.
- Breast ultrasound, a radiation-free tool that evaluates the breast and can find cancers a mammogram may have missed.
- Breast MRI, a radiation-free test that is paired with a contrast injection and takes 30 to 45 minutes. It is the most sensitive test, and the most expensive.
“Breast MRI has not been validated as an appropriate screening tool for women of average risk, or with risk based on breast density alone,” Dr. Gass explains.
Susan Koelliker, MD, director of diagnostic imaging at Women & Infants, adds that “Studies have shown that there is variability between different radiologists, and differences even when read by the same radiologist. The question is should this assessment become more standardized and potentially computer assisted.”
However, knowing that breast density is often not uniform in the breast, she adds a computer-generated method might misrepresent the nuance. A combination of human and computerized efforts might seem an ideal synergy but such systems are expensive and would need to be reimbursed.
“Before we recommend embarking on yet another layer of costly technology for patients, we need to be sure there are robust outcomes that warrant this expense,” Dr. Gass says.