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

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.