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SPIO-enhanced MRI for differentiating metastatic from reactive hyperplastic lymph nodes in breast cancer: diagnostic
Tao Wu1, Angela Wu2, Hui Xiong3
1Department of Cardiology, The Second Affiliated Hospital of Nanchang University, Nanchang, Jiangxi, China.
Background:
Accurate assessment of lymph node status is essential for staging and treatment planning in breast cancer. Conventional morphological imaging criteria have limited sensitivity and specificity. Superparamagnetic Iron Oxide (SPIO)-enhanced MRI offers a functional imaging alternative exploiting macrophage-mediated iron uptake. This study evaluated the diagnostic performance of SPIO-enhanced MRI in differentiating metastatic from reactive hyperplastic lymph nodes and explored the association between MRI signal characteristics and Vascular Endothelial Growth Factor C (VEGF-C) expression.
Methods:
Sixty female breast cancer patients (January-May 2024) underwent preoperative plain and SPIO-enhanced MRI (Resovist, 0.2 mL/kg, 12-h delay). Among 112 harvested lymph nodes, Hematoxylin and Eosin staining, Prussian Blue staining, and VEGF-C immunohistochemistry were performed. The Percentage of Signal Intensity Loss (PSIL) was calculated on T2*-weighted images. The primary diagnostic analysis was patient-level using mean PSIL with receiver operating characteristic analysis.
Results:
Of 112 lymph nodes from 60 patients, 47 were metastatic and 65 reactive hyperplastic. Reactive nodes showed marked signal attenuation (mean PSIL 64.7 ± 12.0%) compared with metastatic nodes (11.6 ± 7.8%; p < 0.001). Patient-level ROC analysis yielded an area under the curve of 0.84 (95% CI: 0.73-0.95). At a data-derived optimal cutoff of 42% (Youden index), sensitivity was 83%, specificity 85%, positive predictive value 80.0%, negative predictive value 87.2%, and overall diagnostic accuracy 84.0%. Histopathological Prussian Blue grading supported differential iron uptake patterns between groups. High VEGF-C expression (≥++) was more prevalent in metastatic than hyperplastic nodes (85.1% vs. 12.3%; p < 0.001). PSIL showed a moderate inverse correlation with VEGF-C grade (Spearman r = -0.67; p < 0.001).
Conclusion:
SPIO-enhanced MRI demonstrated favorable diagnostic performance for differentiating metastatic from reactive hyperplastic lymph nodes at the patient level. The imaging characteristics were associated with supportive histopathological findings and VEGF-C expression patterns. These findings warrant validation in larger, multicenter studies using currently available iron oxide agents.