Nonpalpable breast masses: evaluation by US elastography

Abstract

Objective: To compare the diagnostic performances of conventional ultrasound (US) and US elastography for the differentiation of nonpalpable breast masses, and to evaluate whether elastography is helpful at reducing the number of benign biopsies, using histological analysis as a reference standard.

Materials and methods: Conventional US and real-time elastographic images were obtained for 100 women who had been scheduled for a US-guided core biopsy of 100 nonpalpable breast masses (83 benign, 17 malignant). Two experienced radiologists unaware of the biopsy and clinical findings analyzed conventional US and elastographic images by consensus, and classified lesions based on degree of suspicion regarding the probability of malignancy. Results were evaluated by receiver operating characteristic curve analysis. In addition, the authors investigated whether a subset of lesions was categorized as suspicious by conventional US, but as benign by elastography.

Results: Areas under the ROC curves (Az values) were 0.901 for conventional US and 0.916 for elastography (p = 0.808). For BI-RADS category 4a lesions, 44% (22 of 50) had an elasticity score of 1 and all were found to be benign.

Conclusion: Elastography was found to have a diagnostic performance comparable to that of conventional US for the differentiation of nonpalpable breast masses. The authors conclude that BI-RADS category 4a lesions with an elasticity score of 1 probably do not require biopsy.

Fig. 1

Classification of elasticity scores. A. Score of 1 (E1) indicated that entire lesion was evenly shaded in green. B. Score of 2 (E2) indicated that hypoechoic lesion had mosaic pattern of green and blue. C. Score of 3 (E3) indicated that peripheral portion of lesion was green, and that its central portion was blue. D. Score of 4 (E4) indicated that entire lesion was blue, but that its surrounding area was not included. E. Score of 5 (E5) indicated that both entire hypoechoic lesion and its surrounding area were blue.

Fig. 2

Transverse conventional US and elastographic images of infiltrating ductal carcinoma in 48-year-old woman. A. Conventional US showed 1.1 cm ill-defined hypoechoic mass with mild posterior acoustic shadowing. B. By elastography, entire mass and its surrounding area over margin (white region of interest) were blue, indicating no strain. Final assessment was BI-RADS category 4b by conventional US and score of 5 (E5) by elastography.

Fig. 3

Transverse conventional US and elastographic images of fibrocystic changes in 65-year-old woman. A. Conventional US showed 0.5 cm irregular hypoechoic mass. B. By elastography, mass (white region of interest) appeared green. Final assessment was of BI-RADS category C4a by conventional US and score of 1 (E1) by elastography.

Fig. 4

Receiver operating characteristic curves for conventional US and elastography. Areas under curves were almost same for both conventional US and elastography (0.901 and 0.916, respectively), which was not significantly different (p = 0.808).