Objective: To determine the diagnostic accuracy of axillary US as a preoperative investigation by comparing it with the histology outcome of nodal status.

Methods: This validation analysis was conducted in Mater Misericordia university hospital, Dublin Ireland form Feb 2007 to Feb 2015. All female patients with impalpable axillary lymph node and histology proven unifocal breast cancer between ages 18 to 75 years were included. Patients with the diagnosis of breast cancer were followed with Ultrasound imaging and results in Picture Archiving and communication system (PACS) and histology was confirmed using the patient center data base in both preoperative and postoperative course of breast cancer, including both sentinel lymph nodes and axillary lymph nodes.

Results: A total of 625 patients had axillary ultrasound (US) to assess the preoperative axillary nodal status with mean age of 56±12 years. cN0 was diagnosed in 469 (75%) cases, cN1 in 136 (21.8%) cases and cN2 in 20 (3.2%) cases. After negative axillary ultrasound cN0 pathology shows positive pN2 and pN3 disease in 14 (2.9%) cases with the NPV of 97.01%. Axillary ultrasound had shown cN1 disease in 136 cases with the pathology outcome of pN2 and pN3 in 41 (30.14%) cases with the negative predictive value (NPV) of 69.85%. The overall sensitivity and specificity of the axillary US in detection of the positive node was 51.6% and 92.8% with PPV of 82.69% and NPV of 74.2%.

Conclusion: Axillary US is a useful modality for screening of breast cancer patients. The negative US findings exclude the presence of advanced nodal disease. However, it cannot accurate distinguish between pN1 and pN2 or pN3 nodal disease.

Keywords: Axillary ultrasound, Axillary lymph nodes, Breast cancer.