Developing Asymmetries at Mammography: A Multimodality Approach to Assessment and Management

Abstract

A developing asymmetry is a focal asymmetry that is new or increased in conspicuity compared with the previous mammogram. It is challenging to evaluate, as it often looks similar to fibroglandular tissue at mammography. A developing asymmetry should be viewed with suspicion because it is an uncommon manifestation of breast cancer. Diagnostic mammography forms the foundation of diagnostic evaluation of a developing asymmetry and begins with additional spot compression, lateral, and/or rolled views to evaluate and localize it in three-dimensional space. Digital breast tomosynthesis can aid in evaluation by improving radiologists' sensitivity and specificity, as well as allowing localization of the lesion. Once the developing asymmetry has been fully characterized and localized with diagnostic mammography, targeted ultrasonography (US) should be performed to identify potentially benign causes of the developing asymmetry or identify a target for biopsy. However, lack of a US correlate should not preclude biopsy of a developing asymmetry. Diagnostic breast magnetic resonance imaging can be used in a minority of cases for problem solving or biopsy planning if no US correlate is identified and stereotactic biopsy is not feasible. The purpose of this article is to review the definition of developing asymmetry, describe the multimodality diagnostic tools available to the radiologist for evaluation of this challenging entity, and review the various causes, both benign and malignant.

Developing asymmetry in a screening mammogram: A cautionary tale of a missed cancer

“…Mammographic asymmetries frequently resemble normal fibroglandular tissue, having interspersed fat and lacking convex margins . They account for 6% of non‐palpable, screen‐detected cancers, but represent 27% of missed cancers and are the second most common cause of false negative screening recall assessments .…”

“…An asymmetry and focal asymmetry have similar appearances, being identified on one and both views respectively. A developing asymmetry is a focal asymmetry, not previously present or increasing in size and conspicuity …”

“…Asymmetry and developing asymmetry are seen on 3.3% and 0.16% of screening mammograms respectively . An asymmetry is highly likely to be benign, with the likelihood of malignancy reported at 1.8% .…”

“…Asymmetry and developing asymmetry are seen on 3.3% and 0.16% of screening mammograms respectively . An asymmetry is highly likely to be benign, with the likelihood of malignancy reported at 1.8% . However, 12.8% of the developing asymmetries identified on screening are malignant and therefore these findings require biopsy …”

“…Mammographic asymmetries frequently resemble normal fibroglandular tissue, having interspersed fat and lacking convex margins. 1 They account for 6% of non-palpable, screen-detected cancers, 2 but represent 27% of missed cancers 3 and are the second most common cause of false negative screening recall assessments. 4 The BI-RADS fifth edition categorizes asymmetries occupying less than one quadrant according to visualization on one or more projections and the presence or absence of (a) (b) interval change.…”