Shear wave elastography versus strain elastography to identify benign superficial lymph nodes: sonographic assessment with histopathological confirmation

Abstract

Background Differentiation between benign and malignant superficial lymph nodes (LNs) presents clinical dilemma. No specific criteria are established with conventional ultrasound to make a distinction. We aimed to study the added value of shear wave velocity (SWV) measurement with acoustic radiation force impulse (ARFI) and strain elastography (SE) to identify benign superficial LNs. The study included 115 superficial LNs subjected to conventional ultrasonography, 4-scale strain elastography and shear wave velocity measurement using ARFI. Histopathological analysis was obtained for all examined nodes. Results SE correctly diagnosed 89.3% of the reactive and 92.2% of the metastatic LNs and erroneously diagnosed 72.7% of the lymphoma LNs as being benign. Overall sensitivity, specificity, PPV, NPV and accuracy were 74.4%, 73%, 85.3%, 57.4% and 73.9%, respectively. The receiver operating curve analysis of SWV measurement using ARFI revealed a cut-off value of ≥ 2.70 m/sec to recognize malignant LNs and to obtain best sensitivity (88.5%) and specificity (89.2%) (Area under the curve: 0.819, 95% confidence interval (CI): 0.744 and 0.894). The PPV, NPV and accuracy were 94.5%, 78.6% and 88.7%, respectively. As compared to SE, ARFI boosted the diagnostic accuracy of lymphoma LNs from 27.3 to 68.2% and showed better specificity and NPV to identify benign LN as contrasted to SE. Conclusions SE could be adequate to differentiate reactive from metastatic LN but not from Lymphomas. Shear wave elastography is a reasonable imaging modality to identify benign lymph nodes. ARFI at a cut-off value of < 2.7 m/sec was superior to SE and the best B-mode features.