Breast Cancer and Mammography

Screening mammography is performed in Women without symptoms and is the key to detection of Breast Cancer before a lump can be identified on physical examination. Early detection is critical to diagnosing Breast Cancer at a curable stage. Diagnostic Mammograms are performed in Women with lumps or other significant breast symptoms.

Mammograms have a 15 to 20% false negative rate. One key factor is breast density. The state of Illinois requires that health facilities performing Mammograms notify Women if they have dense breast tissue. About 50 percent of Women have dense breasts. False negative results occur more often among younger Women because they are more likely to have dense breasts. Overall, breasts are composed of fatty and fibroglandular tissue. Fibroglandular tissue is white on the Mammogram and fat is dark; the more fibroglandular tissue in the breast the more dense the Mammogram will be. Because fibroglandular tissue and Breast Cancer have similar density, dense breast tissue may limit detection of Breast Cancer. However, signs of cancer may be detectable in cases with dense tissue. Additional screening tests with ultrasound or MRI may be performed in Women with dense tissue to supplement mammography. Another contributing factor to the false negative rate is that interpretation skills of radiologists vary. It is not just that a Mammogram was performed; it is how the study was interpreted and whether comparison was made to prior Mammograms to evaluate for changes. Misinterpretation of Mammograms can result in Delayed Diagnosis.