Dual-mode 3D shear wave elastography with qualitative and quantitative assessment improves diagnosis of inguinal lymph node metastasis.

Background: Inguinal lymph node (ILN) metastasis significantly affects prognosis and treatment strategies in patients with gynecological malignancies. Conventional ultrasound (US) provides morphological assessment but has limited sensitivity for detecting early metastatic changes. Three-dimensional shear wave elastography (3D-SWE) enables volumetric stiffness assessment with multiplanar visualization and may overcome the planar limitations of two-dimensional SWE (2D-SWE). This study aims to determine whether 2D-SWE or 3D-SWE improves the diagnostic performance of US for identifying ILN metastasis and to compare the complementary value of qualitative pattern analysis and quantitative elasticity metrics. Methods: We retrospectively included 131 ILNs from 125 women with gynecological malignancies who underwent conventional US, 2D-SWE, and 3D-SWE. Qualitative color pattern analysis and quantitative elasticity parameters (Emax, Emean) were evaluated alone and in combination with US features. Histopathology served as the reference standard. Diagnostic performance was assessed using receiver operating characteristic (ROC) analysis and compared with DeLong tests. Results: Of the 131 ILNs, 72 (55.0%) were malignant and 59 (45.0%) were benign. Among the three orthogonal 3D-SWE planes, the coronal plane demonstrated superior diagnostic performance across both qualitative and quantitative assessments. As standalone methods, qualitative coronal 3D-SWE achieved an area under the curve (AUC) of 0.846, while quantitative coronal-plane Emax achieved an AUC of 0.847, with no significant difference between them (P=0.920). When combined with conventional US, qualitative coronal 3D-SWE achieved the highest overall diagnostic performance [AUC 0.891, 95% confidence interval (CI): 0.834-0.947], with a sensitivity of 86.11% and a specificity of 88.05%, significantly outperforming conventional US alone (P<0.001). Among quantitative models, sagittal-plane Emax combined with US showed the best performance (AUC 0.858, 95% CI: 0.795-0.921), with a sensitivity of 87.50% and a specificity of 79.19%, also significantly better than conventional US alone (P<0.001). There was no significant difference between the best qualitative and quantitative combined models (AUC 0.891 Conclusions: In this retrospective study, integrating 3D-SWE with conventional US significantly improved the detection of ILN metastasis through multiplanar qualitative and quantitative elasticity assessment. The coronal plane demonstrated superior diagnostic performance across both qualitative and quantitative assessments, and qualitative and quantitative 3D-SWE offered comparable incremental value when combined with US. These findings support 3D-SWE as a useful adjunct to conventional US for preoperative ILN evaluation in gynecological malignancies, particularly vulvar and vaginal cancers, in which ILN status is a key prognostic determinant.