Lymph Node Elastography: Differentiation of Benign and Metastatic Lesions
The Role of Elastography in Lymph Node Assessment
According to Diagnostic Ultrasound: Musculoskeletal (Griffith, 2025), blood flow indices (resistance index, pulsatility index) have limited value due to significant overlap with reactive values. In this context, shear wave elastography (SWE) serves as an auxiliary method for differentiating malignant from benign lymph nodes.
Diagnostic Efficacy of SWE
According to the same source, SWE demonstrates the following metrics in differentiating metastatic from benign lymph nodes:
| Metric | Value |
|---|---|
| Sensitivity | 82% |
| Specificity | 80% |
| Accuracy | 81% |
Principle of Stiffness Assessment
Elastography measures tissue stiffness. SWE is less operator-dependent than strain elastography and allows both qualitative and quantitative assessment with color maps in m/s or kilopascals (kPa) (Griffith, 2025). Typically, malignant lesions exhibit increased stiffness, whereas the proportion of benign lesions with increased stiffness is significantly lower (analogous to EFSUMB data for other locations).
Methodology and Limitations
According to the standard methodology, lesion boundaries are determined in B-mode (higher spatial resolution and real anatomical contours), and the elastogram is used as a functional stiffness map in the same plane. When calculating the strain ratio, the lesion ROI is placed in the area of maximum stiffness, and the reference ROI is placed in the surrounding tissue at a comparable depth.
It is important to note that elastography is not specific enough to be used as a standalone method for characterizing soft tissue lesions (Griffith, 2025). Strain elastography depends on pressure, depth, and preload, and is subject to artifacts: a hard halo may extend beyond the actual boundaries of the node, and a soft center (necrosis) may 'conceal' part of the lesion.
Additional B-Mode Features
In differentiating lymphadenopathy, grayscale criteria are also considered. For example, lymphoma is characterized by a round shape, well-defined margins without extracapsular spread, loss of normal echogenic hilum (in 75% of cases, except for follicular lymphoma), marked hypoechogenicity, and an intranodal reticular pseudocystic pattern (Griffith, 2025).
Frequently asked questions
What is the diagnostic accuracy of SWE for lymph nodes?
According to Griffith (2025): sensitivity 82%, specificity 80%, accuracy 81% in differentiating malignant from benign lymph nodes.
Can elastography be used as a standalone method?
No. Elastography is not specific enough for standalone characterization of lesions and serves as a complement to standard ultrasound (Griffith, 2025).
What should be outlined first — the lesion in B-mode or on the elastogram?
First B-mode (higher resolution and real contours), then the elastogram as a functional stiffness map in the same plane.
How does SWE differ from strain elastography?
SWE is less operator-dependent and allows qualitative and quantitative assessment (m/s or kPa). Strain elastography depends on pressure, depth, preload, and is subject to artifacts.
Where to place the ROI when calculating the strain ratio?
Lesion ROI — in the area of maximum stiffness (or encompass the entire lesion according to the device protocol), reference ROI — in the surrounding tissue at a comparable depth.