Is routine intraoperative frozen-section examination of sentinel lymph nodes in breast cancer worthwhile?

Background: Routine intraoperative frozen section (FS) of sentinel lymph no des (SLN) can detect metastatic disease, allowing immediate axillary dissec tion and avoiding the need for reoperation. Routine FS is also costly, incr eases operative time, and is subject to false-negative results. We examined the benefit of routine intraoperative FS among the first 1000 patients at Memorial Sloan Kettering Cancer Center who had SLN biopsy for breast cancer . Methods: We performed SLN biopsy with intraoperative FS in 890 consecutive breast cancer patients, none of whom had a back-up axillary dissection plan ned in advance. Serial sections and immunohistochemical staining for cytoke ratins were performed on all SLN that proved negative on FS. The sensitivit y of FS was determined as a function of (1) tumor size and (2) volume of me tastatic disease in the SLN, and the benefit of FS was defined as the avoid ance of a reoperative axillary dissection. Results: The sensitivity of FS ranged from 40% for patients with T1a to 76% for patients with T2 cancers. The volume of SLN metastasis was highly corr elated with tumor size, and FS was far more effective in detecting macromet astatic disease (sensitivity 92%) than micrometastases (sensitivity 17%). T he benefit of FS in avoiding reoperative axillary dissection ranged from 4% for T1a (6 of 143) to 38% for T2 (45 of 119) cancers. Conclusions: In breast cancer patients having SLN biopsy, the failure of ro utine intraoperative FS is largely the failure to detect micrometastatic di sease. The benefit of routine intraoperative FS increases with tumor size. Routine FS may not be indicated in patients with the smallest invasive canc ers.