Breast Edema Score on Magnetic Resonance Imaging and Its Association with Molecular Subtypes of Breast Cancer

Abstract

Breast edema is an important magnetic resonance imaging (MRI) finding in breast cancer, reflecting alterations in lymphatic drainage, microvascular permeability, and tumor-associated inflammatory changes. This review summarizes the mechanisms and MRI appearance of breast edema, the breast edema score (BES), and its relationship with the molecular subtypes of breast cancer. On T2-weighted imaging, edema may appear in peritumoral, prepectoral, subcutaneous, or diffuse patterns, and increasing edema extent may indicate more aggressive tumor biology. Available evidence suggests significant associations between BES and molecular phenotype, with higher edema scores reported more frequently in HER2-positive and triple-negative tumors, whereas lower scores are more often associated with luminal subtypes. Breast edema and peritumoral edema have also been linked to lymphovascular involvement, axillary nodal disease, inflammatory changes, and adverse prognostic features. Multiparametric breast MRI, combining T2-weighted imaging with dynamic contrast-enhanced and diffusion-weighted sequences, provides complementary structural and functional information. Overall, BES represents a promising non-invasive imaging biomarker that may contribute to molecular subtype prediction, risk stratification, and preoperative assessment, although standardized scoring criteria and prospective validation remain necessary before routine clinical implementation.