Sensitivity, Specificity, and Accuracy of Ultrasound, Mammography, and 18F-FDG PET/CT in Diagnosing Breast Cancer Metastasis to Axillary Lymph Nodes: A Single-Center Experience

<i>Background and Objectives</i>: Axillary lymph node (ALN) status is one of the most important prognostic factors in breast cancer. Numerous studies have evaluated less invasive methods for accurate staging. To investigate the diagnostic performance of ultrasound (US), mammography, and ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT) in predicting axillary lymph node metastasis in breast cancer patients. <i>Materials and Methods</i>: Axillary involvement detected by US, mammography, and ¹⁸F-FDG PET/CT was analyzed in patients who underwent axillary dissection. Preoperatively, 365, 318, and 85 of 557 patients were evaluated with US, mammography, and PET/CT, respectively. The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy of each imaging modality were calculated. <i>Results</i>: The sensitivity, specificity, PPV, NPV, and accuracy of US were 33.3%, 97.5%, 94.4%, 51.0%, and 57.8%, respectively. False-negative US findings were more frequent in T1 (84.6%) and N1 (76.3%) tumors (<i>p</i> < 0.001 for both). For mammography, these values were 12.9%, 97.74%, 88.89%, 44.67%, and 52.9%, while for ¹⁸F-FDG PET/CT they were 72.5%, 100%, 100%, 67.65%, and 82.5%, respectively. <i>Conclusions</i>: Ultrasound remains useful for evaluating axillary lymph node involvement in advanced breast cancer but is insufficient for early-stage disease.