There has been much in the news lately regarding dense breast tissue and the concerns regarding risk of breast cancer as well as the inability of routine mammography to detect breast cancers in women with dense breast tissue.
First of all, it is important to understand what is being discussed when you hear the term “dense breast tissue”. The breast is normally composed of fat and glandular tissue – the higher proportion of glandular tissue, the denser the breast. It is important to note that “lumpy” breast tissue is not the same as dense breast tissue – density is determined by the appearance on a mammogram, not by feel. The denser your breast tissue, the more “white” the breast will appear on a mammogram; women with primarily fatty breasts will have a mammogram that appears darker. Digital mammograms (compared to older film screen mammograms) have an easier time seeing through dense breast tissue, but all mammograms are limited in their ability to see through dense tissue and identify cancers, as cancers usually appear as dense white lumps on a mammogram. In general approximately 10-20% of breast cancers are missed by standard mammography – that percentage can approach 40-50% in women with dense breast tissue.
It was previously thought that mammograms simply had a harder time detecting breast cancer in women with dense breast tissue. However, we now know that a woman with dense breast tissue does have an increased risk for developing breast cancer and this is the subject of intense research. There are many factors that influence breast density including age, hormone levels, genetics, age at first pregnancy and number of pregnancies, use of hormone replacement therapy, overall body weight – just to name a few. And as younger women naturally have denser breast tissue, that does not mean that women in their 20’s and 30’s have an increased risk of breast cancer – in fact the risk of breast cancer increases with increasing age; it is hard to sort out when the increased risk as it relates to breast density develops.
Unfortunately, it is sometimes difficult for a woman to know if she has dense breast tissue – remember it is not the same as “lumpy” breasts. When you undergo a mammogram, the radiologist is required to make a comment regarding breast density in his or her report. However, patients often do not receive the radiologist’s report. Mammography performance and reporting in this country is regulated by the FDA, through the Mammography Quality Standards Act, and currently it is required that patients receive a “lay letter” – a report written in layperson terms that gives a basic summary of the findings and recommendations. Your physician who ordered the mammogram will receive the official report with a notation of density.
Several states (including California) have now passed legislation requiring that patients be informed of their breast density. While I agree that patients certainly have a right to their full and un-edited test results, it is unfortunate that legislation was required to ensure that women receive their complete test results. Federal legislation is pending regarding this matter.
If you have dense breasts, what should you do? We know that MRI, and certain forms of ultrasound, especially automated whole-breast ultrasound, can be very helpful in evaluating women with very dense breast tissue. While I do recommend these studies for some patients, realize that there are no formal guidelines by either the American College of Radiology or the American Cancer Society regarding breast imaging for women with dense breast tissue, unless the woman is also considered to be in a high-risk category (for example those with a strong family history of breast cancer). Some of these tests are not covered by insurance. Also realize that MRI and ultrasound also have some limitations when imaging dense breast tissue – there is no perfect method of evaluation.
Newer methods of mammography such as tomosynthesis and contrast-enhanced mammography are showing promise, but studies are still being performed; these exams may also expose a woman to higher doses of radiation and/or a contrast material injection.
My recommendation is that women speak to their doctors. Ask if your breast tissue is considered dense, and if so, would you benefit from additional testing. Stay tuned for more information as newer imaging techniques which improve the rate of cancer detection in women with dense breast tissue are being developed.
Dr. Attai was one of the physicians invited to testify before the California Legislature in support of SB 1538, which was eventually signed by Governor Brown, requiring that mammography facilities in California inform patients if they have dense breast tissue on mammogram.
By Deanna Attai