# Breast MRI in the Assessment of Internal Thoracic Lymph Nodes: Morphodynamic and Functional Criteria for Detection of Metastatic Lymph Nodes

## TL;DR

This study identifies MRI features that help distinguish cancerous from non-cancerous lymph nodes in breast cancer patients, potentially improving diagnosis and staging.

## Contribution

The study introduces morphological and functional MRI criteria to differentiate metastatic from non-metastatic internal thoracic lymph nodes in breast cancer.

## Key findings

- Metastatic lymph nodes showed significantly larger size, volume, and lower ADC values compared to non-metastatic nodes.
- Morphological and functional MRI parameters achieved over 90% sensitivity and specificity in distinguishing metastatic lymph nodes.

## Abstract

Introduction: Metastasis to internal thoracic artery lymph nodes (ITLNs) occurs in a substantial proportion of patients with breast carcinoma and is associated with adverse prognosis. Despite its clinical importance, standardized imaging criteria for ITLN assessment are lacking. This study aimed to evaluate morphological and functional MRI features that differentiate metastatic from physiological ITLNs in breast cancer patients.

Methods: In this retrospective single-center study, 34 patients with histologically confirmed invasive breast carcinoma and detectable ITLNs on breast MRI were included. Sixteen patients had metastatic ITLNs (confirmed histologically or by fluorodeoxyglucose positron emission tomography), while 18 patients had non-metastatic ITLNs with imaging stability on follow-up. All patients underwent breast MRI, including dynamic contrast-enhanced (DCE)-MRI and diffusion-weighted imaging (DWI). Morphological parameters (short axis, long axis, short-to-long axis ratio, volume, surface area, and compactness) and functional parameters (apparent diffusion coefficient (ADC) and positive enhancement integral (PEI)) were analyzed and compared between groups.

Results: Metastatic ITLNs demonstrated significantly larger short and long axis diameters, greater volume and surface area, lower compactness, and significantly lower ADC values compared with non-metastatic ITLNs (all p < 0.0001). The short-to-long axis ratio and PEI showed smaller differences between groups and were less discriminatory. The ADC values were significantly lower in metastatic ITLNs, reflecting increased cellularity. Cut-off values for multiple parameters demonstrated high diagnostic performance, with sensitivities and specificities exceeding 90%.

Conclusions: Morphological MRI parameters, particularly lymph node size, volume, surface area, compactness, and ADC values, provide reliable criteria for distinguishing metastatic from physiological ITLNs in breast cancer patients. Incorporation of these morpho-functional MRI features into routine breast MRI assessment may improve diagnostic accuracy and staging. Larger prospective multicenter studies are warranted to validate these findings and establish standardized imaging protocols.