Pre-operative staging of the axilla in primary breast cancer. By redefining the abnormal appearing node can we reduce investigations without affecting overall treatment?

Primary axillary clearance (ANC) is currently performed based on cytology from abnormal appearing node(s) without considering extent of involvement. We assessed correlation between nodal burden and nodal appearance. 439 invasive breast cancer cases underwent axillary ultrasound (AUSS) with nodal scoring [UN2-normal (n = 293), UN3-indeterminate (n = 84), UN4-suspicious (n = 29), and UN5-replaced (n = 34)]. Fine needle aspiration cytology (FNAC) of all UN3, UN4 & UN5 nodes was performed. 64 cases had nodal metastases identified pre-operatively, proceeding to primary ANC. 375 cases underwent sentinel lymph node biopsy (SLNB), 64 of whom were found to have nodal metastases. Likelihood of metastases and nodal burden was related to AUSS score. >50% of malignant UN4 & UN5 scored nodes had ≥4 metastases compared to 19% of UN3 nodes. Most UN3 nodes are either not involved or have low metastatic burden which may be better served by SLNB alone. Redefining our FNAC nodal threshold could potentially avoid additional ANC morbidity and reduce pre-operative workload.