Breast Lesions: Evaluation with Shear Wave Elastography, with Special Emphasis on the “Stiff Rim” Sign

Purpose To analyze the diagnostic performance of shear wave elastography (SWE) in differentiating between benign and malignant breast lesions, with special emphasis on the value of the “stiff rim” sign, as compared with conventional ultrasonography (US). Materials and Methods For this ethics committee–approved retrospective study, all patients provided verbal informed consent for the analysis of their imaging data. A total of 193 consecutive women (age range, 18–82 years; mean age, 46 years) with 193 breast lesions (56 malignant, 137 benign) were included. The stiff rim sign, a qualitative SWE feature, was evaluated at the display setting of less than 180 kPa and at 180 kPa. The quantitative SWE features were assessed. Sensitivity, specificity, the area under the receiver operating characteristic curve (Az), and positive and negative likelihood ratios were calculated for conventional US features, for SWE features, and for combined conventional US and SWE features. Results Among all qualitative and quantitative SWE features, the stiff rim sign at the display setting (<180 kPa) showed the highest Az (0.918; 95% confidence interval [CI]: 0.870, 0.953), which was comparable to that for conventional US (0.891; 95% CI: 0.838, 0.931) (P = .40). The combination of the stiff rim sign at less than 180 kPa and conventional US features, with a positive likelihood ratio of 12.23 (95% CI: 11.5, 13.0) and a negative likelihood ratio of 0.02 (95% CI: 0.003, 0.1), yielded the highest Az (0.982; 95% CI: 0.951, 0.995)—higher than those for conventional US only and for any single SWE feature alone (P < .001 for all)—and yielded higher sensitivity (98.2% [55 of 56]; 95% CI: 90.4%, 100.0%) and similar specificity (92.0% [126 of 137]; 95% CI: 86.1%, 95.9%) compared with conventional US (P < .001 and P = .58, respectively). With use of this combination, the rate of recommendation of benign lesions for interventional procedures would decrease from 56.9% (78 of 137) (on the basis of conventional US features) to 15.3% (21 of 137), and 100.0% (56 of 56) (95% CI: 93.6%, 100.0%) malignant lesions would be correctly selected for biopsy. Conclusion Adding SWE features, especially the stiff rim sign at the display setting (<180 kPa), to conventional US has the potential to improve the differentiation of breast lesions. © RSNA, 2014