Axillary node evaluation and biopsy: Predictors of malignancy based on sonographic morphology and mode of detection

The purpose of this study was to evaluate various morphologic features of axillary nodes on ultrasound (US) in predicting malignancy and estimate the incidence of malignancy in axillary nodes based on their imaging mode of detection.

A retrospective review of all percutaneous US-guided biopsies on axillary nodes performed at our institution between 1/1/2019-09/30/2021 was performed. Sonographic morphologic features of the biopsied node, imaging mode of detection and size of primary breast malignancy were correlated with malignancy.

There were 224 malignancies detected in a total of 594 patients who underwent an axillary node biopsy. The positive predictive value (PPV) was significantly associated with the extent of nodal cortical thickening (p < 0.0001). The PPV of malignancy was significantly higher in nodes which lacked a normal hilum (0.61 vs 0.23). The PPV of malignancy in nodes detected on screening mammography (18.8%) or MRI (15.8%) was much lower than those detected on diagnostic imaging, by palpation or on CT/PET (48.4%, 43.8% and 65.3% respectively). Of all screening detected nodes in patients with no history of malignancy and mild cortical thickening, only 2 (4.3%) demonstrated malignancy.

Morphology of axillary nodes on sonography is vital in predicting nodal metastasis. Cortical thickness > 5 mm and/or absence of a normal hilum had the highest PPV for metastatic disease. Using clinical history in conjunction with imaging findings will help improve accuracy of axillary nodal biopsies, especially for incidental nodes detected on screening.