In vitro B-mode ultrasonographic criteria for diagnosing axillary lymph node metastasis of breast cancer

Axillary lymph node status is an important factor for staging and treatment planning in breast cancer. Our study was performed in vitro on a node-by-n ode basis to evaluate the ability of B-mode ultrasonographic images to dist inguish metastatic from nonmetastatic nodes. Immediately prior to histologi c examination, individual dissected axillary nodes were scanned in a water bath using a 10 MHz B-mode ultrasonographic transducer. Four B-mode feature s (size, circularity, border demarcation, and internal echo) were evaluated for their ability to distinguish metastatic from nonmetastatic lymph nodes . Lymph node metastasis was indicated by (1) a large size (i.e., a length o f the longest axis 10 mm or greater); (2) a circular shape (i.e., the ratio of the shortest axis to the longest axis between 0.5 and 1.0); (3) a sharp ly demarcated border compared with surrounding fatty tissue; and (4) a hypo echoic internal echo, with obliteration of the fatty hilum. The sensitivity and specificity were compared for all combinations of features. We examine d 84 histologically characterized axillary nodes from 27 breast cancer pati ents, including 64 nonmetastatic and 20 metastatic nodes. Of the criteria c ited, circular shape was the best single feature for distinguishing metasta tic from nonmetastatic nodes (sensitivity, 65%; specificity, 73%). The best combination of sensitivity (85%) and specificity (73%) was obtained using the criterion that a lymph node contained cancer when at least three positi ve features were present. The present in vitro study demonstrated that the sensitivity and specificity of B-mode ultrasonography for diagnosing lymph node metastasis were lower than 90%. Therefore, B-mode ultrasonography ly m ay not be an optimal noninvasive screening method for diagnosing axillary l ymph node metastasis in breast cancer patients, particulary under in vivo c linical conditions.