Objectives <p>To investigate MRI-based breast edema patterns as biomarkers of tumor aggressiveness and their predictive value for pathological response to neoadjuvant chemotherapy (NAC) in invasive breast cancer.</p> Materials and methods <p>This retrospective study evaluated 235 female patients (mean age, 52 ± 12 years) with biopsy-proven invasive breast cancer who underwent pre-NAC breast MRI. After excluding 19 patients (10 for inadequate image quality, 9 for post-biopsy imaging), 216 patients were analyzed. Breast edema score (BES) was independently assessed by two radiology residents to evaluate interobserver agreement. Subsequently, a breast radiologist reviewed all cases to establish the definitive dataset. The differences in clinicopathological characteristics between the two groups and between different BES were compared.</p> Results <p>Interobserver agreement for BES classification was very high (92.6% concordance). Edema presence correlated significantly with larger tumor size (<i>p</i> = 0.001), higher histological grade (<i>p</i> = 0.001), axillary lymph node metastasis (<i>p</i> = 0.015), hormone receptor negativity (<i>p</i> &lt; 0.001), lymphovascular invasion (<i>p</i> = 0.031), and elevated Ki-67 (<i>p</i> = 0.001). Higher BES groups (BES 2-4) showed stronger associations with aggressive features: tumor size (<i>p</i> &lt; 0.001), grade (<i>p</i> = 0.022), hormone receptor negativity (<i>p</i> = 0.001), non-luminal subtypes (<i>p</i> = 0.001), and intratumoral necrosis (<i>p</i> = 0.002). Neither edema nor BES predicted pathological response to NAC (<i>p</i> = 0.999, <i>p</i> = 0.299).</p> Conclusion <p>BES and edema are robust imaging biomarkers of tumor aggressiveness but demonstrate no predictive value for NAC response. MRI-based edema scoring holds clinical relevance for noninvasive tumor phenotyping and risk stratification in breast cancer management.</p> Key Points <p><Emphasis Type="BoldItalic">Question</Emphasis> <i>Can MRI-based breast edema patterns predict tumor aggressiveness and pathological response to neoadjuvant chemotherapy in invasive breast cancer patients, aiding noninvasive risk stratification?</i></p> <p><Emphasis Type="BoldItalic">Findings</Emphasis> <i>BES correlates with aggressive tumor features (larger size, higher grade, hormone negativity; all p &lt; 0.050 but shows no predictive value for NAC response (p = 0.299)</i>.</p> <p><Emphasis Type="BoldItalic">Clinical relevance</Emphasis> <i>BES serves as a practical imaging biomarker for risk stratification and tumor phenotyping, guiding individualized therapy. However, it shows no utility in predicting NAC response, emphasizing the need for complementary predictive tools in treatment planning</i>.</p> Graphical Abstract <p></p>