Shear wave elastography as a supplement tool in the assessment of unsuspicious axillary lymph nodes in patients undergoing breast

Shear wave elastography as a supplement tool in the assessment of unsuspicious axillary lymph nodes in patients undergoing breast

REVIEWED BY Jacqui Roots | ASA SIG: Emerging Technologies

REFERENCE | Authors: Riku Togawa, Leah-Larissa Binder, Manuel Feisst, Richard G Barr, Sarah Fastner, Christina Gomez, André Hennigs, Juliane Nees, André Pfob, Benedikt Schäfgen, Anne Stieber, Fabian Riedel, Jörg Heil, Michael Golatta

WHY THE STUDY WAS PERFORMED

This study assessed the stiffness of unsuspicious axillary lymph nodes by utilising shear wave elastography. It is known that an increased stiffness is a predictor for malignancy, but first we must understand what normal stiffness values should be. The authors aimed to quantify the stiffness values of physiological, healthy lymph nodes, including the hilum, cortex and surrounding fatty tissue, to have a better understanding of normal.

HOW THE STUDY WAS PERFORMED

One hundred and seventy-seven lymph nodes (within a total of 177 axillae of 175 patients) were measured with standard ultrasound and shear wave elastography. The Siemens Acuson S2000 and S3000 machines were used, equipped with virtual touch tissue imaging quantification (VTIQ) software. This returns a shear wave velocity in m/s as the stiffness value. Stiffer tissues return faster velocities.

A random representative lymph node was selected in level I or II of the axilla. The lymph node had to have good accessibility and absence of malignancy signs (cortical thickening, rounded node, complete or partial effacement of fatty hilus, or pathological colour Doppler images). The elasticity values from the hilum, cortex and surrounding fatty tissue were measured three times and documented.

This observational study was performed prospectively in a single centre. Written informed consent was obtained from each patient.

WHAT THE STUDY FOUND

The velocity of the hilus showed a higher stiffness compared to the cortex of the same lymph node. The mean shear wave velocity of the cortex was 1.9 m/s (0.34SD), 2.02 m/s (0.37) in the hilus, and 1.75 m/s (0.38SD) in the surrounding fatty tissue. There was no difference detected between the right and left axilla at any of the three locations.

There was a statistically significant difference between the shear wave velocities of the hilus and the fatty tissue, as well as between the cortex and the hilus. The size of the lymph node did not correlate with the shear wave velocities; neither did the depth of the lymph nodes.

“When performing SWE routinely in the breast, extending the examination to the axilla can be performed using the same probe and software while the patient can maintain the same position.”

RELEVANCE TO CLINICAL PRACTICE

Shear wave elastography can be used as a supplementary tool for assessing the stiffness of lymph nodes of the axilla and takes approximately 1 to 2 minutes per side. This study has evaluated healthy, unsuspicious lymph nodes and provided reference values for the hilus, cortex and surrounding fatty tissue. SWE is a reliable tool regardless of the depth and size of the lymph node.