Background. We report the use of a thorough intraoperative sentinel lymph node (SLN) biopsy screening procedure for patients with small NO breast tumors. Methods. Sixty-eight consecutive female patients with monofocal stage I or "small" stage II (ie, 2.1-3.0 cm) NO tumors received intraoperative SLN screening according to a procedure on the basis of comprehensive histologic analysis and cytokeratin immunohistochemical determination (CkID) of adjacent frozen sections of the SLN taken at 50-μm cutting levels. Results. The maximum duration of intraoperative analysis including CkID was 40 minutes. Positive SLN were found in 15/68 (22%) patients (always in a single node); they included 5 instances of micrometastasis and 3 of carcinomatous lymphangitis. In the 14 patients who underwent axillary lymph node dissection, no further metastasis was found at histologic analysis or CkID. SLN positivity correlated with histologic type (P = .044), intratumoral or peritumoral vascular invasion (P <.001 ) and Mib1 score (P = .042). Conclusions. It is possible for an experienced team to perform intraoperative SLN screening for T1 or small T2 NO breast tumors with frozen sections taken at 50-μm cutting levels. This procedure facilitates identification of micrometastasis, as well as of carcinomatous lymphangitis to help understand the biologic implications of these small lesions in the long term. SLN positivity appears to correlate with histologic type, intratumoral/peritumoral vascular invasion and Mib1 score.
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