Accuracy of intraoperative imprint cytology for sentinel lymph node evaluation in the treatment of breast carcinoma: A 6-year study

BACKGROUND. The current report provides results from a large retrospective analysis of intraoperative imprint cytology performed on axillary sentinel lymph nodes (IICN) removed over the course of 2137 breast surgeries (4905 lymph nodes). It is hoped that these results may serve as benchmarks for those interested in using this technique. METHODS. The current study included 2078 patients with T1-2 invasive breast carcinoma who underwent sentinel lymph node biopsy (SLNB) and IIC^N. Lymph nodes were bivalved, imprinted, stained with Diff-Quik (Baxter Diagnostics, McGaw Park, IL), and reviewed by a cytopathologist. A positive intraoperative diagnosis led to immediate complete axillary lymph node dissection (CALND). On final pathology, lymph nodes found to be negative on hematoxylin and eosin staining were submitted for cytokeratin staining. RESULTS. Of the 2137 cases for which SLNB was performed, 673 were found to have positive lymph node status on final pathology. Of these 673 cases, 359 were identified by IIC^N, resulting in a sensitivity rate of 53.3%. The specificity and overall accuracy rates for this technique were 99.5% and 85.0%, respectively. In IDC cases, IIC^N had a sensitivity rate of 55.5%, compared with 38.7% in ILC cases. Based on these results, the reoperative CALND rate was calculated to be approximately 14.7%, with 54.5% of these reoperative procedures being performed for cases in which lymph nodes positive only for micrometastases were found. Macrometastasis-positive lymph nodes that went undetected by IIC^N were present in only 154 of the 2137 cases examined (7.2%). CONCLUSIONS. IIC^N accurately predicts final lymph node status in 85.0% of patients. Although the accuracy of this technique varies with tumor size and type, IIC^N remains a time-efficient and cost-effective adjunct to SLNB.