In vitro sonographic evaluation of sentinel lymph nodes for detecting metastasis in breast cancer: comparison with histopathologic results.

OBJECTIVE: To assess the accuracy and the effectiveness of in vitro sonography of sentinel lymph nodes (LNs) for differentiating benignity from metastasis during breast cancer operations. METHODS: Two hundred twenty-two fresh sentinel LNs obtained during surgery were examined by in vitro sonography to detect metastasis in 47 patients with breast cancer. Sonographic criteria of malignant LNs were defined as uneven cortical thickness of greater than 3 mm in depth, round hypoechoic nodes, and the absence of an echogenic hilum. Histopathologic results were correlated with those obtained by the sonographic study. Statistical analysis was performed with a kappa value to evaluate the accuracy of in vitro sonography of sentinel LNs. RESULTS: On sonographic examination, 190 (85.6%) of the 222 sentinel LNs were benign. Among the 190 benign LNs, in only 8 (4.2%) was the presence of metastasis pathologically proved, which indicated focal micrometastasis in the cortex. Thirty-two sentinel LNs were sonographically positive. In 19 (59.4%) of the 32 sentinel LNs, metastasis was pathologically confirmed. The remaining 13 sonographically positive LNs (40.6%) did not reveal any histologically malignant cells. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were 70.4%, 93.3%, 59.4%, 95.7%, and 90.5%, respectively. CONCLUSIONS: The in vitro sonographic evaluation of the sentinel LNs during breast cancer operations may be a reliable method of predicting nodal metastasis and may be helpful in deciding the extent of LN dissection.