In vitro high-resolution helical CT of small axillary lymph nodes in patients with breast cancer: correlation of CT and histology.

OBJECTIVE This study seeks to determine whether high-resolution in vitro helical CT can show the internal structure of small axillary nodes and to establish the CT characteristics of benign versus metastatic axillary nodes in patients with breast cancer. SUBJECTS AND METHODS We obtained in vitro helical CT images of 212 nodes excised from 19 patients with breast cancer. The longest mean size was 5.9 mm, and the range was 0.5 to 26.5 mm. The hilar and cortical characteristics, the size, and the ratio of the longest axis to the shortest axis were evaluated. CT findings were correlated with histologic findings. RESULTS Pathologic assessment of excised nodes with a central low-density hilum visualized on CT showed arteries, veins, lymphatic sinuses, and fatty tissue. A peripheral high-density cortex on CT contained mostly lymphatic tissue. Abnormal (eccentric, irregular) cortices were observed in malignant nodes (p<0.0001). Marked differences were observed among the proportions of benign and malignant nodes when the ratio of the longest axis to the shortest axis was less than 2 and an abnormal cortex was observed. CT could also detect extracapsular lymph node extension. CONCLUSION In vitro high-resolution helical CT can detect the internal structure of small nodes. Morphologic changes detected on helical CT help distinguish benign from malignant nodes.