Preoperative Axillary Ultrasound in the Selection of Patients With a Heavy Axillary Tumor Burden in Early-Stage Breast Cancer: What Leads to False-Positive Results?

OBJECTIVES: To determine whether imaging and clinicopathologic features could predict false-positive axillary ultrasound (US) results in the selection of patients with breast cancer who had a heavy axillary tumor burden (≥3 tumor-involved nodes).

METHODS: Among 788 patients with histologically confirmed invasive breast cancer at Ruijin Hospital from October 2014 to September 2015, 162 patients (cT1-T2, cN0) with 167 axillae had suspicious axillary US findings. Ultrasound findings were considered suspicious for metastasis if cortical thickening of greater than 3 mm or effacement of the fatty hilum was present. The false-positive rate of suspicious axillary US results for identifying 3 or more positive lymph nodes in the final pathologic examination was calculated. Univariate and multivariate analyses were used to evaluate imaging and clinicopathologic factors related to the false-positive results.

RESULTS: Axillary US showed a false-positive rate of 60.5% (101 of 167) in the patients with breast cancer and a heavy nodal burden. By logistic regression analyses, we found false-positive axillary US results more frequently in patients who had a T1 stage tumor (P = .005), an estrogen receptor/progesterone receptor-negative tumor (P < .001), solitary suspicious nodes identified on axillary US (P < .001), and a cortical thickness of the most suspicious lymph node of 3.5 mm or less (P = .015).

CONCLUSIONS: Imaging and clinicopathologic features can be used to identify axillae with less than 3 metastatic nodes in patients with early-stage breast cancer who have positive axillary US results. In the post-American College of Surgeons Oncology Group Z0011 trial era, conducting a secondary evaluation either clinically or by axillary imaging before the use of a US-guided biopsy of suspicious nodes can potentially avoid the additional morbidity of axillary lymph node dissection and reduce the preoperative workload.