When breast tissue is more dense, it becomes harder for doctors to see changes to the tissue with standard mammography techniques. Until recently, most women whose breast tissue was dense were not told that their breasts could be hiding tumors and were not sent for additional imaging or followup tests.
Some of those women, like Nancy Cappello, learn later on that the mammogram missed a significant tumor. Cappello found out that she had late stage breast cancer that had not been detected due to the dense tissue in her breasts. She was outraged that doctors knew the dense tissue could be hiding tumors, yet did nothing to inform her that in spite of her clean bill of health from the mammogram, she could still be at significant risk of breast cancer.
Cappello took her story to the Connecticut legislature, which enacted a law requiring doctors to tell patients if their breast tissue was dense. This is no rare problem—up to 40 percent of mammography patients today have dense breast tissue, and the denser tissue cannot be felt for in a manual examination: like small tumors and tiny fractures, the denser tissue can only be revealed by x-ray imaging.
Changing guidelines on mammography and new trends in breast cancer detection have led patient rights groups to advocate for laws about the disclosure of dense breast tissue. However, doctors warn that more imaging may not necessarily be the right solution.
When women with dense breast tissue follow their clear mammogram up with additional ultrasound imaging, there is a greater likelihood that tumors will be detected. However, ultrasound is not the first line imaging technique for breast cancer detection for a reason: it also generates high numbers of false negatives. Each of these false negatives requires a full biopsy, and this is both stressful and expensive for the women involved.
The American Medical Association published a study earlier in 2012 showing that over 90 percent of additional suspicious tissues found with ultrasound turned out to be false positives rather than actual tumors. There has not yet been research conducted on whether the types of tumors that are found only with ultrasound are cancerous or which types of tumors they are.
Doctors also note that there are several types of tumors that mammograms detect better than ultrasound, leading some to speculate that having the additional imaging done, and mandating the warnings, is overkill that could cause women unnecessary stress and worry. However, that hasn't stopped legislatures in four more states (Texas, Virginia, New York, and California) from passing laws requiring disclosure of dense breast tissue.
In the months and years to come, research should reveal whether the types of tumors found on ultrasound but missed by mammograms are dangerous, and whether the new disclosure laws lead to better detection and cure rates for breast cancer.
Sources: Nytimes.com, nih.gov