Sentinel lymph node biopsy in breast cancer: the role of micrometastasis

Intraoperative sentinel lymph node biopsy is widely used in patients with early-stage breast cancer for staging the axilla. The conventional analysis of the SLN has classically been performed by frozen section or touch imprint with a rapid H&E (hematoxylin and eosin) staining. Because of the risk of false-negative results, it has been replaced by the one-step acid amplification (OSNA) assay, a molecular diagnostic assay for the detection of cytokeratin 19 mRNA expression. Due to the controversial for the use of OSNA to evaluate the SLN because of its cost-effective and the lack of consensus to perform or avoid a lymphadenectomy when there is micrometastasis, we analyze 410 patients subjected to SLN biopsy in Hospital Puerta de Hierro, Madrid (Spain). Of the total of nodes, 223 (54.4 %) were processed throughout frozen-section examination and imprint cytology and 187 (45.6 %) throughout OSNA. The specificity of the frozen-section histological examination was of 100 %, with a sensitivity of 83.33 % (95 % CI 73.07–93.60). Of the 40 patients with definitive micrometastasis in the SLN, axillary dissection was performed in 90 % of the patients, with subsequent positive affectation in four of them (11.11 %). Based on our result and taking into account that 10 % of the lymphadenectomy performed after micrometastasis are positive, we do not believe that lymphadenectomy should be avoided after N(mi+) is detected in a SLN.