Clinical Utility and Limitations of Ultrasound‐Guided Axillary Lymph Node Fine‐Needle Aspiration Cytology in Breast Cancer Management

ABSTRACT Background Accurate axillary staging is critical for selecting appropriate treatment strategies in breast cancer. Ultrasound (US) and ultrasound‐guided fine‐needle aspiration cytology (US + FNAC) are widely used to evaluate axillary lymph nodes. The study assessed the diagnostic accuracy of US and US + FNAC and examined whether axillary dissection (AD) is necessary in patients with positive US + FNAC findings. Methods We analyzed 646 axillae from 642 breast cancer patients who underwent surgery at Hiraka General Hospital between 2013 and 2024. All patients underwent axillary US, and US + FNAC was performed on morphologically suspicious nodes. Sensitivity, specificity, PPV, and NPV of US and US + FNAC were determined using postoperative pathology as the reference standard. The number of nodal metastases was compared between patients undergoing primary surgery and those receiving primary systemic therapy (PST). Results In the primary surgery group ( n = 516), US sensitivity, specificity, PPV, and NPV were 30.9% (38/123), 94.1% (370/393), 62.3% (38/61), and 81.3% (370/455), respectively. Corresponding values for US + FNAC were 80.6% (29/36), 100% (22/22), 100% (29/29), and 75.9% (22/29). US + FNAC showed significantly higher sensitivity and PPV than US alone. Among US + FNAC‐positive cases, 55.2% (16/29) had ≥ 3 metastatic nodes, compared with 6.9% (2/29) of negative cases. In the PST group ( n = 130), US sensitivity was ≤ 88.1% (37/42), and US + FNAC sensitivity was ≤ 92.6% (25/27). Of the 46 US + FNAC‐positive patients, 45.7% (21/46) became node‐negative after PST, whereas 26.1% (12/46) had ≥ 3 positive nodes. Conclusion US + FNAC improves diagnostic accuracy for axillary staging; however, standard AD may constitute overtreatment in some FNAC‐positive patients. Selective de‐escalation of axillary surgery should therefore be considered.