Getting a False Positive

Mammography screening, like all screening tests, carries the possibility of a false positive.

Mammography results may appear to be abnormal even though no cancer is present. Getting a false-positive result causes a great deal of anxiety. It is usually followed by more testing such as a biopsy, which can have risks. Follow up tests may be painful and prolong the anxiety during the weeks between the original false-positive diagnosis and the pathology report following a biopsy.

Most women are initially relieved to hear that a biopsy shows no cancer, than angry at having been put through the expense, pain and anxiety of additional tests. Some decide not to have future mammograms while others dismiss the false-positive as a fluke.

However, anyone with a previous false-positive might want to read an article in the May 2 issue of the Journal of the National Cancer Institute, which paints a different picture of the possible significance of false-positives.

The article states that a recent population study suggests that a false-positive finding on mammography points to a greater chance of breast cancer long-term, possibly because of underlying pathology or initial misclassification.

The study noted that the risk of breast cancer remained significantly elevated from 6 to more than 12 years after a false-positive test result.

The study examined outcomes for 58,003 women, ages 50 to 69, who participated in Copenhagen’s population-based mammography screening program from 1991 to 2005. At that time, false-positive test rates ranged from 5.6% to 1.4%.

My von Euler-Chelpin, PhD, of the University of Copenhagen, and colleagues reported that women with any type of false-positive test faced an adjusted 67% higher risk of breast cancer after a false-positive test than women who had only negative screens  They recommended encouraging women with false-positive tests to continue to receive regular screenings even though it could cause extra anxiety.

“Women with false-positive tests manifest suspicious mammographic patterns in their breast tissue, including tumor-like masses, suspicious microcalcifications, skin thickening or retraction, recently retracted nipples, distortions, asymmetric densities, or suspicious axillary lymph nodes,” von Euler-Chelpin and colleagues noted.

“Despite a thorough assessment to exclude malignancies at baseline, these suspicious patterns in breast tissue may eventually develop into detectable cancer.

Even with newer screening methods, women with false-positive tests should be encouraged to use regular mammographic screening because a false-positive test may indicate underlying pathology that could result in breast cancer.”

Sources: Journal of the National Cancer Institute, Von Euler-Chelpin M, et al “Risk of breast cancer after false-positive test results in screening mammography” J Natl Cancer Inst 2012; 104; DOI: 10.1093/jnci/djs176.