Role of ultrasound-guided fine-needle aspiration of indeterminate and suspicious axillary lymph nodes in the initial staging of breast carcinoma

BACKGROUND. Ultrasound (US) is more sensitive than physical examination alone in determining axillary lymph node involvement during preliminary staging of breast carcinoma. Due to occasional overlap of sonographic features of benign and indeterminate lymph nodes, fine-needle aspiration (FNA) of sonographically indeterminate/suspicious lymph nodes can provide a more definitive diagnosis than US alone. This study was undertaken to determine the diagnostic accuracy of US-guided FNA of indeterminate/suspicious/metastatic-appearing axillary lymph nodes during the initial staging of breast carcinoma. METHODS. The cytology of 103 cases of US-guided FNA of nonpalpable indeterminate/suspicious/metastatic-appearing lymph nodes was compared with the final histopathologic status of the entire axilla after axillary dissection. The final axillary lymph node status was categorized as either negative when all lymph nodes were negative for metastasis or positive when there was evidence of metastasis in one or more lymph nodes. The sensitivity, specificity, diagnostic accuracy, and false-negative rate of US-guided FNA of nonpalpable axillary lymph nodes in the preliminary staging process were calculated. RESULTS. In 51 of 103 cases (49.5%), the US-guided FNA and histopathology were both positive for metastasis. In 24 of 103 cases (23.3%), both were negative. The apparent false-positive FNA in 16 (15.5%) cases was explained by the complete response of the metastatic lymph nodes to neoadjuvant chemotherapy in the interval between FNA and axillary dissection. In 12 cases (11.6%), US-guided FNA was negative, but metastasis was seen in histologic sections. All cases with three or more lymph nodes with metastatic disease and 93% of those with metastatic deposit measuring more than 0.5 mm were detected by US-guided FNA. The probability of detecting lymph nodes with smaller metastatic deposit measuring less than 0.5 cm was 44%. The overall sensitivity of US-guided FNA was 86.4%, the specificity was 100%, the diagnostic accuracy was 79.0%, the positive predictive value was 100%, and the negative predictive value was 67%. CONCLUSIONS. US-guided FNA of nonpalpable indeterminate and suspicious axillary lymph nodes is a simple, minimally invasive, and reliable technique for the initial determination of axillary lymph node status in breast carcinoma. The common causes of discrepancy between the initial and final axillary lymph node status include failure to visualize all lymph nodes during US examination, small-sized metastases, and preoperative neoadjuvant chemotherapy.