Differentiation of Metastatic and Non-Metastatic Mesenteric Lymph Nodes by Strain Elastography in Surgical Specimens

Abstract

Purpose: To investigate if strain elastography could differentiate between metastatic and non-metastatic mesenteric lymph nodes ex-vivo.

Materials and Methods: 90 mesenteric lymph nodes were examined shortly after resection from 25 patients including 17 patients with colorectal cancer and 8 patients with Crohn’s disease. Ultrasound-based strain elastography was performed with a linear probe. Tissue hardness in lymph nodes was assessed using visual scales and measuring the strain ratio. B-mode characteristics were also recorded. Pathological diagnosis with grading of fibrosis served as the reference standard.

Results: 20 lymph nodes were metastatic and 70 lymph nodes were non-metastatic. The strain ratios of metastatic and non-metastatic lymph nodes were significantly different (1.83 vs. 1.42, p = 0.021). The VAS scale (0 – 100) for tissue hardness gave higher mean values for metastatic than non-metastatic nodes, but the difference was not significant (65.5 vs. 55.0, p = 0.055). There was no difference between lymph nodes in Crohn’s and non-metastatic cancer specimens. The metastatic lymph nodes were significantly more fibrotic than the non-metastatic lymph nodes by the ordinal fibrosis score (0 – 3). In an ROC analysis, quantitative strain imaging was not superior to the measurement of the short-axis diameter of lymph nodes in differentiating metastatic from non-metastatic mesenteric lymph nodes ex-vivo.

Conclusion: Strain elastography is correlated to fibrosis in lymph nodes and a significant difference was observed on a group level using the strain ratio. Due to measurement overlap, individual mesenteric lymph nodes could not be identified accurately as metastatic or not in this ex-vivo model by strain imaging alone.

Zusammenfassung

Ziel: Untersuchung, ob die Strainelastografie zwischen metastatischen und nicht-metastatischen mesenterialen Lymphknoten (LK) ex-vivo differenzieren kann.

Material und Methoden: 90 mesenteriale LK wurden kurz nach der Resektion von 25 Patienten (17 Patienten mit kolorektalem Karzinom und 8 Patienten mit Morbus Crohn) untersucht. Die sonografische Strainelastografie wurde mit einer linearen Sonde durchgeführt. Die Gewebesteifigkeit in LK wurde durch visuelle Skalen und durch Messung der Strainratio bestimmt. Die B-Bild-Charakteristik wurde ebenfalls aufgenommen. Die pathologische Diagnose mit Graduierung der Fibrose diente als Referenzstandard.

Ergebnisse: 20 LK waren metastatisch und 70 LK waren nicht-metastatisch. Der Unterschied der Strainratios von metastatischen (1,83) und nicht-metastatischen LK (1,42) war signifikant (p = 0,021). Die VAS-Skala (0 – 100) für Gewebesteifigkeit ergab höhere Mittelwerte für metastatische Knoten (65,5) im Vergleich zu nicht-metastatischen LK (55,0), der Unterschied war jedoch nicht statistisch signifikant (p = 0,055). Es gab keinen Unterschied zwischen LK aus Proben bei Morbus Crohn und nicht-metastatischem Karzinom. Die metastatischen LK waren signifikant fibrotischer als nicht-metastatische Knoten in der Fibrose-Rangskala (0 – 3). In der ROC-Analyse war die quantitative Straindarstellung nicht besser als die Messung des Kurzachsendurchmessers der LK im Hinblick auf die Ex-vivo-Differenzierung zwischen metastatischen und nicht-metastatischen mesenterialen LK.

Schlussfolgerung: Die Strainelastografie korreliert signifikant mit der Fibrose in Lymphknoten. Aufgrund der überlappenden Messungen konnten in diesem Ex-vivo-Modell bei ausschließlicher Straindarstellung einzelne mesenteriale LK nicht als metastasiert oder nicht metastasiert identifiziert werden.

Key words

lymphatic - mesentery - ultrasound - metastases - adenocarcinoma

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