Redefining ultrasound appearance criteria of positive axillary lymph nodes

To determine objective criteria for ultrasonography (US) appearance in the diagnosis of abnormal axillary lymph nodes (ALNs) and to assess retrospectively their accuracy in preoperative staging of patients with Breast Imaging Reporting and Data System (BI-RADS) Category 5 breast lesion.

US-guided axillary fine-needle aspiration biopsy (FNAB) was performed for preoperative staging of BI-RADS Category 5 lesions in breast cancer patients seen at the Ottawa Regional Women's Breast Health Centre. Retrospectively, ALN morphology was classified into 3 categories based on US appearance: mass-like appearance, focal nodular cortical thickening (FNCT), and diffuse cortical thickening (DCT), the latter 2 with fatty hilum preservation and cortical thickening greater than 2 mm. Cytologic results from the FNAB were compared with axillary lymph node dissection (ALND) or sentinel lymph node procedure (SLNP), when available. Retrospective image-based classification was performed blind to pathology results and analyzed with Pearson's correlation coefficient, receiver operating characteristic (ROC) curves, and chi-square and Hosmer-Lemeshow tests against the cytologic ground truth.

Eighty-six ALNs in 84 patients were sampled with an 18-gauge needle under US guidance. The number of passes per sample was related to adequate sampling of positive ALNs having mass-like morphology but not DCT or FNCT (p < 0.001). The most frequent morphologic presentation of the 86 ALNs was mass-like appearance of lymph nodes (45%), followed by DCT (35%) and FNCT (20%). Metastatic involvement was found in 34 (87%) of 39 ALNs that were mass-like, in 9 (53%) of 17 ALNs with FNCT, and in 9 (30%) of 30 ALNs with DCT. The kappa agreement between FNAB and ALND or SLNP was 0.64 for mass-like lymph nodes, 0.7 for lymph nodes with DCT, and 1.0 for FNCT. Overall sensitivity and specificity were 94% and 89%, respectively, with a positive predictive value of 97% and negative predictive value of 80%.

Using a 2-mm threshold, FNCT and DCT warrant US-guided FNAB by an experienced radiologist as much as do mass-like lymph nodes. When biopsy is positive, axillary dissection can be performed and the sentinel node technique avoided.