Evaluation of intraoperative frozen section diagnosis of sentinel lymph nodes in breast cancer

Background: Intraoperative frozen sections (FS) of sentinel lymph nodes (SLNs) can be used to detect metastatic disease, allowing immediate axillary lymph node dissection (ALND). However, pathological inconsistency in the SLNs diagnosis is sometimes encountered when the results of FS and permanent sections are compared. The purpose of this study was to reveal the usefulness and limitations of FS for the diagnosis of SLNs in patients with breast cancer. Methods: We reviewed the results for 569 patients with breast cancer at stage 0-II who underwent a sentinel node biopsy between February 1998 and December 2002. SLNs were analyzed using standard FS procedures and a single section stained with hematoxylin and eosin was examined. Patients determined to have positive SLNs based on the results of the FS diagnosis immediately underwent ALND. Permanent sections were later prepared from the remaining frozen tissues and examined using hematoxylin and eosin staining without additional immunohistochemical staining. Results: Seven cases (1%) with atypical cells were found in the FS diagnosis intraoperatively, which were counted as 'negative' by the following analysis. The final pathology results showed metastasis in the SLN sections in 159 patients (28%), of whom 26 were diagnosed as negative by the FS diagnosis. Accuracy, specificity and the false-negative rate were 95, 100 and 16%, respectively. The mean size of the nodal metastases in the false-negative cases was significantly smaller than that in the true-positive cases (n = 72) (P < 0.01). False-negative rates for T1b, T1c and T2 were 33, 19 and 14%, respectively. The rate of micrometastasis in T1 (43%) was significantly higher than that of T2 (13%) (P < 0.01). Conclusions: FS diagnosis for SLNs is reliable. Patients with negative SLNs by the FS diagnosis can avoid reoperation for ALND. However, FS may fail to detect micrometastases, especially in cases with small tumors.