Image-Guided Localization Techniques for Metastatic Axillary Lymph Nodes in Breast Cancer; What Radiologists Should Know

SIMPLE SUMMARY: Breast cancer is the most frequent cancer affecting women, and axillary lymph nodes (ALNs) are the most common initial site of metastatic spread. In patients with positive ALNs undergoing neoadjuvant chemotherapy (NACT), it is necessary to localize and identify the lymph node metastases in order to perform less invasive axillary surgery, such as targeted axillary dissection (TAD). In this setting, the choice of the most appropriate localization methods is crucial to correctly orientate the removal of the pathological ALNs. This is more important considering that ALNs can become non-palpable after NACT. National Comprehensive Cancer Network (NCCN) guidelines also suggest their possible use in a non-NACT setting, particularly in patients candidate to SLNB with limited numbers of positive ALNs in whom ALNs have been biopsied. ABSTRACT: Targeted axillary dissection (TAD) is an axillary staging technique after NACT that involves the removal of biopsy-proven metastatic lymph nodes in addition to sentinel lymph node biopsy (SLNB). This technique avoids the morbidity of traditional axillary lymph node dissection and has shown a lower false-negative rate than SLNB alone. Therefore, marking positive axillary lymph nodes before NACT is critical in order to locate and remove them in the subsequent surgery. Current localization methods include clip placement with intraoperative ultrasound, carbon-suspension liquids, localization wires, radioactive tracer-based localizers, magnetic seeds, radar reflectors, and radiofrequency identification devices. The aim of this paper is to illustrate the management of axillary lymph nodes based on current guidelines and explain the features of axillary lymph node markers, with relative advantages and disadvantages.