Impact of the sentinel node frozen section result on the probability of additional nodal metastases as predicted by the MSKCC nomogram in breast cancer.

OBJECTIVE Sentinel lymph node frozen section is used to obviate the need for a second operation in breast cancer patients with involved nodes. However, the overall sensitivity, specificity and accuracy of sentinel lymph node frozen section are debated, and the impact of sentinel lymph node frozen section positivity on the risk of additional nodal metastases is not known and was the focus of this investigation. METHODS We used our hospital record system to identify 176 sentinel lymph node biopsies done out of 354 cases of Stage T1-3N0 breast cancers managed from 2005 to 2007 and evaluated the sentinel lymph node frozen section results against the predictions of additional nodal metastases based on the Memorial Sloan-Kettering Breast Cancer Nomogram which is a validated tool for this purpose. RESULTS Sentinel lymph node metastases size was an independent predictor of sentinel lymph node frozen section sensitivity and those with macrometastases had 15 times the odds (odds ratio, 15.4; 95% confidence interval, 3.4-69.1) of having a true-positive frozen section when compared with those with micrometastases. The breast cancer nomogram predicted that the latter patients have a very low probability of additional nodal metastases with a median probability at 10% (inter-quartile range, 7-14%). CONCLUSIONS A negative sentinel lymph node frozen section is also associated with a low probability of additional nodal metastases. Additional prognostic factors in the breast cancer nomogram are of little clinical impact because the most predictive factor in the nomogram is the method of detection.