Comparative Diagnostic Performance of Breast MRI and PET/CT in Axillary Nodal Staging of Breast Cancer

Objective: To perform a direct, paired comparison of breast magnetic resonance imaging (MRI) and positron emission tomography/computed tomography (PET/CT) for preoperative axillary lymph node staging in patients with breast cancer. Methods: In this retrospective, single-center study, female patients with histologically confirmed breast cancer who underwent both breast MRI and PET/CT prior to surgery were included. Histopathological findings obtained before neoadjuvant therapy served as the reference standard. MRI assessments were based on predefined morphological and functional criteria, whereas PET/CT interpretation relied on focal 18F-fluorodeoxyglucose uptake. Imaging findings were dichotomized on a per-patient basis. Diagnostic performance metrics were calculated, and paired comparisons were conducted using McNemar’s exact test. Results: Among 104 patients, 58 (55.8%) had histopathologically confirmed axillary metastasis. MRI demonstrated a significantly higher sensitivity than PET/CT (96.6% vs. 68.6%) and superior overall diagnostic accuracy (92.3% vs. 81.7%). In contrast, PET/CT exhibited higher specificity (98.1% vs. 87.0%). Agreement with histopathology was very good for MRI (κ=0.83) and good for PET/CT (κ=0.66). A paired analysis showed that all PET-positive cases were also identified by MRI, whereas MRI detected additional metastases not identified by PET/CT (P < 0.001). Conclusion: Breast MRI provides superior sensitivity and overall diagnostic performance, whereas PET/CT offers excellent specificity in axillary staging. Although neither of the modalities replaces surgical nodal assessment, their distinct diagnostic characteristics may inform individualized preoperative risk stratification and multidisciplinary management strategies.