Two-View Asymmetry

This chapter reviews key imaging features, protocols, pitfalls, differential diagnoses, and management recommendations for a two-view asymmetry. A focal asymmetry is a small amount of fibroglandular dense tissue seen on two views that is asymmetric compared to the contralateral breast. A global asymmetry is defined as a large focal asymmetry that extends beyond one breast quadrant. A developing asymmetry is defined as a focal asymmetry that is new, denser, or larger when compared to prior mammograms. In general, an asymptomatic global asymmetry is considered a normal variant. In contrast, a developing asymmetry should be evaluated with greater suspicion. Topics discussed in the chapter are superimposition, global asymmetry, developing asymmetry, and triangulation.

Impact of prior mammograms on combined reading of digital mammography and digital breast tomosynthesis

Background Although digital breast tomosynthesis (DBT) is an emerging technique yielding higher sensitivity and specificity compared to digital mammography (DM) alone, relative contribution of prior mammograms on the interpretation of DBT combined with DM has not been investigated. Purpose To retrospectively compare the diagnostic performances of DM, DM + DBT, and DM + DBT with prior mammograms. Material and Methods Three breast radiologists independently reviewed images of 116 patients with 24 cancers in the sequential order of DM, DM + DBT, and DM + DBT with prior mammograms using Breast Imaging Reporting and Data System (BI-RADS) assessment categories. Results The average areas under the receiver operating characteristic curve (AUC) of DM, DM + DBT, and DM + DBT with prior mammograms were 0.712, 0.777, and 0.816, respectively. Adding prior mammograms did not significantly affect the AUC of DM + DBT ( P = 0.108), whereas adding DBT significantly increased the AUC of DM ( P = 0.009). Sensitivity for DM, DM + DBT, and DM + DBT with prior mammograms was 58.3%, 69.4%, and 69.4%, and specificities were 84.1%, 85.9%, and 93.8%, respectively. Addition of DBT significantly increased the sensitivity ( P = 0.0090) of DM. Prior mammograms significantly improved the specificity of DM + DBT ( P = 0.0004), whereas adding prior mammogram did not affect sensitivity of DM + DBT ( P = 1.000). Conclusion DBT significantly increases the overall sensitivity and diagnostic performance of DM. Prior mammograms significantly increase the specificity of DM + DBT but have no significant effect on sensitivity and overall diagnostic performance.