Abstract
BACKGROUND: The evaluation of sentinel lymph nodes (SLNs) from a patient with lobular breast cancer is challenging. Metastatic lobular cancer is difficult to identify in SLNs because of its low-grade cytomorphology and its tendency to resemble lymphocytes. Intraoperative imprint cytology (IIC) is a rapid, reliable method for evaluating SLNs intraoperatively. We sought to reexamine our experience with this technique in the identification of invasive lobular breast cancer SLN metastases. METHODS: A retrospective review of a prospectively maintained database of IIC results of 1010 SLN mapping procedures for breast cancer was performed. From this cohort we reviewed SLN cases of lobular cancer. The SLNs were evaluated intraoperatively by bisecting the SLN. Imprints were made of each cut surface and stained with hematoxylin and eosin (H&E) and Diff-Quik. Permanent sections were evaluated with up to 4 H&E-stained levels and cytokeratin immunohistochemistry. IIC results were compared with final pathologic results. RESULTS: A total of 67 cases of pure invasive lobular cancer were identified. The sensitivity was 71%, specificity was 100%, and accuracy was 92%. No statistically significant differences in sensitivity, specificity, or accuracy were identified between the intraoperative detection of lobular carcinoma vs ductal carcinoma. The specificity has remained the same since 2004. However the accuracy (82% vs 92%; P = .09) and sensitivity (52% vs 71%; P = .02) has improved since 2004. CONCLUSIONS: As we have previously shown, the sensitivity and specificity of IIC in evaluating lobular carcinoma is feasible and accurate. IIC continues to be a viable alternative to frozen section for intraoperative evaluation.