Real-Time Tissue Elastography as Promising Diagnostic Tool for Diagnosis of Lymph Node Metastases in Patients with Malignant Melanoma: A Prospective Single-Center Experience

Abstract

Background: Real-time tissue elastography is a new, noninvasive method in ultrasonography, differentiating tissues according to their stiffness. Earlier studies have highlighted this technique as a useful diagnostic tool for the detection of noncutaneous malignancies like breast, prostate and thyroid cancer based on the principle that tumor cells present a higher stiffness compared to the adjacent normal tissue. Objective: The purpose of our study was to investigate the value of real-time tissue elastography for the differentiation of benign and metastatic peripheral lymph nodes (LN) in patients with cutaneous melanoma by comparing this technique with conventional B-mode sonography combined with power Doppler sonography (PDS). Methods: In this prospective study, 36 melanoma patients (23 females and 13 males, mean age 62.7 ± 11.1 years) undergoing LN excision at the Department of Dermatology and Allergy, University of Bonn, were included between July 2011 and July 2012. Real-time tissue elastography was planned prior to surgery and histopathological examination. Elasticity images had been qualitatively scored for the proportion of stiff areas from pattern 1-5 (soft to stiff) on the basis of a newly defined system for LNs. Results: A total of 42 LNs have been removed in 36 patients. Of these 42 LNs, 21 carried melanoma cells and 21 were benign LNs. Significant differences in elastographic patterns were found between metastatic and nonmetastatic LNs. In real-time tissue elastography, 19 (90.5%) of 21 metastatic LNs showed a pattern of 3, 4 or 5. Of all benign LNs, 76.2% had a pattern of 1 or 2 in their elastogram. Sensitivity and specificity of B-mode sonography combined with PDS were 80.9 and 76.2%, respectively, 90.5 and 76.2% for elastography and 95.2 and 76.2% for the combined evaluation. Conclusion: An elastography pattern ≥3 was identified as an independent significant factor, predicting a metastatic LN involvement. The combination of elastography with conventional B-mode sonography has the potential to further improve the differentiation between benign and metastatic peripheral LNs in melanoma patients.