LAUSR

Background Metaplastic breast cancer (MBC), characterized by admixed epithelial, squamous or mesenchymal elements, constitutes <1% of breast cancers and has a poor prognosis but a paradoxically low reported rate of axillary lymph node (LN) involvement. Due to its rarity, data on appropriate axillary management is lacking, prompting this investigation of LN status and outcomes. Methods We identified 41 MBC patients treated at our institution 2001-2011 who were followed for a median of 66 months. Statistical analyses evaluated axillary ultrasound (AUS), fine needle aspiration (FNA), and sentinel LN biopsy (SLNB) in association with LN status. Results Median tumor size was 2.7 cm and 76% were triple-negative. Twenty-three patients (56%) had preoperative AUS: 9 (39%) showed ≥1 suspicious LN, 6 proceeded to LN FNA and 3 were confirmed positive. Six patients had neoadjuvant chemotherapy, including 2 FNA LN+. Ten patients were LN+ at operation. Among 19 patients undergoing AUS and axillary surgery, AUS ± FNA sensitivity was 100% and specificity was 94%. LN positivity correlated with increasing tumor size, grade and angiolymphatic invasion. 16 patients recurred, 63% with distant disease (10/16) and one with isolated axillary disease after a negative SLNB not preceded by AUS. Overall SLNB accuracy was 96% (23/24), but absent preoperative AUS, 1/7 (14%) of SLNBs were falsely negative. Conclusions Our study is the first to specifically address the performance and utility of AUS/FNA and SLNB for MBC patients. AUS/FNA at diagnosis followed by SLN surgery provided accurate nodal staging and critical prognostic information to inform treatment recommendations. We recommend this approach for axillary management of MBC patients.