Axillary Ultrasound: For All, for None, to Diagnose Positive Nodes, or to Support Avoiding Sentinel Lymph Node Biopsy Altogether.

Axillary ultrasound is increasingly utilized for nodal staging preoperatively in patients presenting with invasive breast cancer to provide guidance for preoperative chemotherapy or proceeding directly to surgery. Improvements in ultrasound technology make it possible to assess the nodal burden in order to identify those patients not eligible for ACOSOG Z0011 management. However, its ability to detect metastasis is variable and dependent on operator's skills, size of metastatic deposit, and primary tumor histology subtype. Therefore, sentinel lymph node biopsy is still performed with a normal axillary ultrasound. Current debate questions whether there is a benefit to diagnosing metastasis with ultrasound-guided needle biopsy as this may lead to more axillary node dissections in an era of its decreasing role. In node-positive patients, axillary ultrasound has been preliminarily shown to be helpful in assessing nodal response after preoperative chemotherapy and improve the accuracy of sentinel node dissection which may spare future patients' axillary node dissection. Improvements in axillary ultrasound and other imaging modalities along with predictive models based on tumor biology may make axillary surgery a procedure of the past for many breast cancer patients.