Potential Use of Contrast-Enhanced Ultrasound (CEUS) in the Detection of Metastatic Superficial Lymph Nodes in Melanoma Patients

Abstract

Purpose: Malignant melanoma represents a significant and growing public health burden worldwide. Ultrasonography is the most useful diagnostic modality for regional lymph nodal staging. Because any focal areas of cortical lobulation or thickening-swelling should also be considered as a sign of metastases, we are going to report the usefulness of contrast-enhanced ultrasonography (CEUS) in the differential diagnosis of benign or malignant lymph nodes in patients with malignant melanoma based on blood stream patterns and investigate the diagnostic capability.

Patients and Methods: After the excision of cutaneous melanoma with positive excision margins but with negative sentinel lymph node, 540 patients underwent US of superficial lymph nodes. The inclusion criteria for CEUS consisted of both major signs (absence of the echogenic hilus, round shape, and peripheral capsular vascularity) and minor ones (the presence of focal cortical thickening). The diagnostic capability was evaluated by comparing the cytological findings with the enhancement pattern on CEUS. 

Results: US in combination with CEUS correctly classified 534/540 patients. CEUS applied to lymph nodes with focal cortical thickening on grayscale US confirmed great sensitivity (0.98) and specificity (0.99) but above all, it showed a markedly improved accuracy of 0.99. The likelihood ratios confirmed the good performance of the methods used.

Conclusion: CEUS increases the diagnostic accuracy of US in the differential diagnosis of benign and malignant LNs but it also allows us, when possible, to avoid unnecessary invasive operations such as LN FNAC. Moreover, CEUS may guide FNAC in the case of focal cortical thickening on the basis of hypoperfusion, with a reduction in the number of false negatives and much earlier detection of nodal metastatic foci.

Zusammenfassung

Ziel: Das maligne Melanom stellt ein bedeutendes und weltweit zunehmendes Gesundheitsproblem dar. Die Sonografie ist die nützlichste diagnostische Methode für das Staging der regionären Lymphknoten. Da alle fokalen Areale einer kortikalen Lobulierung, Verdickung oder Schwellung als Zeichen einer Metastasierung angesehen werden sollten, berichten wir über den Nutzen der kontrastverstärkten Ultrasonografie (CEUS) zur Differentialdiagnose gutartiger und maligner Lymphknoten basierend auf den Perfusionsmustern und untersuchen die Diagnosekapazität.

Patienten und Methoden: Nach Entfernung der kutanen Melanome mit positiven Schnitträndern und negativen Wächterknoten wurde bei 540 Patienten eine Sonografie der oberflächlichen Lymphknoten durchgeführt. Die Einschlusskriterien für CEUS bestanden sowohl aus den Hauptzeichen (Fehlen des echoreichen Hilus, runde Form und periphere, kapsuläre Durchblutung) als auch aus einem Nebenzeichen (Auftreten einer Kortexverdickung). Die diagnostische Wertigkeit wurde durch den Vergleich der zytologischen Befunde mit den Perfusionsmustern der CEUS ermittelt.

Ergebnisse: Ultraschall in Kombination mit CEUS klassifizierte 534/540 Patienten korrekt. CEUS bestätigte bei Lymphknoten, die im B-Bild eine fokale Kortexverdickung aufwiesen, eine hohe Sensitivität (0,98) und Spezifität (0,99), darüber hinaus führte CEUS zu einer deutlich verbesserten diagnostischen Genauigkeit von 0,99. Der Likelihood-Ratio-Test bestätigte die gute Leistungsfähigkeit der angewandten Methoden.

Schlussfolgerung: CEUS erhöht die diagnostische Genauigkeit des US bei der Differentialdiagnose gutartiger und maligner Lymphknoten (LN), und erlaubt uns, gegebenenfalls unnötige invasive Eingriffe wie eine Feinnadelaspirationszytologie zu vermeiden. Darüber hinaus kann CEUS die Feinnadelaspirationszytologie bei einer hypoperfundierten fokalen Kortexverdickung stützen, indem diese die Anzahl falsch-negativer Befunde verringert und den wesentlich früheren Nachweis nodaler metastatischer Herde ermöglicht.

Key words

lymphatic - melanoma - metastases - microbubbles - ultrasound

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