US-Guided Fine Needle Aspiration Biopsy Axillary Node US-guided axillary lymph node sampling is the most useful next study performed when axillary imaging is suspicious for metastatic disease [4]. Sampling of abnormal-appearing lymph nodes by US-guided FNA is frequently performed with a 22- or 25-gauge needle and also requires the availability of skilled cytopathologists. False-negative rates are low (< 2%) in experienced hands but may occur, especially with smaller metastatic deposits [143]. Some centers place a clip in the biopsied node to facilitate future image-guided localization of the lymph node at surgical excision after completion of NAC. US-guided axillary FNA has proven high specificity, with a moderate to high sensitivity in the detection of metastatic lymph nodes. A retrospective study of 65 patients compared US-guided FNA results to final surgical pathology in patients with radiographically suspicious lymph nodes and demonstrated high sensitivity, specificity, and positive predicative value (89%, 100% and 100%, respectively) for FNA [144]. A larger meta-analysis of 1,353 patients undergoing axillary lymph node biopsy to detect metastases showed that both FNA and CNB performed well, with sensitivities of 74% and 88%, respectively, and a specificity of 100% for both procedures. Complication rates for FNA were lower than CNB (1% versus 7%, respectively) and were most commonly pain, hematoma, and bruising [142]. Additionally, one prospective study of combined axillary US and FNA in 315 patients with sonographically positive lymph nodes again demonstrated high sensitivity (81%), specificity (100%), and positive predictive value (100%). However, the NPV was low (50%), supporting the need for definitive surgical sampling [145].
Monitoring Response to Neoadjuvant Systemic Therapy for Breast Cancer. US-Guided Fine Needle Aspiration Biopsy Axillary Node US-guided axillary lymph node sampling is the most useful next study performed when axillary imaging is suspicious for metastatic disease [4]. Sampling of abnormal-appearing lymph nodes by US-guided FNA is frequently performed with a 22- or 25-gauge needle and also requires the availability of skilled cytopathologists. False-negative rates are low (< 2%) in experienced hands but may occur, especially with smaller metastatic deposits [143]. Some centers place a clip in the biopsied node to facilitate future image-guided localization of the lymph node at surgical excision after completion of NAC. US-guided axillary FNA has proven high specificity, with a moderate to high sensitivity in the detection of metastatic lymph nodes. A retrospective study of 65 patients compared US-guided FNA results to final surgical pathology in patients with radiographically suspicious lymph nodes and demonstrated high sensitivity, specificity, and positive predicative value (89%, 100% and 100%, respectively) for FNA [144]. A larger meta-analysis of 1,353 patients undergoing axillary lymph node biopsy to detect metastases showed that both FNA and CNB performed well, with sensitivities of 74% and 88%, respectively, and a specificity of 100% for both procedures. Complication rates for FNA were lower than CNB (1% versus 7%, respectively) and were most commonly pain, hematoma, and bruising [142]. Additionally, one prospective study of combined axillary US and FNA in 315 patients with sonographically positive lymph nodes again demonstrated high sensitivity (81%), specificity (100%), and positive predictive value (100%). However, the NPV was low (50%), supporting the need for definitive surgical sampling [145].