Rapid immunohistochemistry enhances the intraoperative diagnosis of sentinel lymph node metastases in invasive lobular breast carcinoma

BACKGROUND. The sensitivity of the intraoperative diagnosis of sentinel lymph 2 node (SLN) micrometastases and the metastases of invasive lobular carcinoma (ILC) is low. The goal of the current study was to assess whether the use of intraoperative, rapid immunohistochistochemistry (IHC) enhances the intraoperative detection of micrometastases and metastases of ILC. METHODS. The sensitivity of the intraoperative diagnosis of SLN metastasis was evaluated in 438 patients when using rapid IHC with a cytokeratin biomarker. The results were compared with those obtained for 557 patients without rapid IHC but with conventional staining. RESULTS. For patients with ILC, the sensitivity of the intraoperative diagnosis was 87% (45 of 52) in the IHC group and 66% (39 of 59) in the non-IHC group (P = 0.02). The sensitivity of the intraoperative diagnosis was similar for patients with other types of invasive cancer regardless of the use of rapid IHC. However, rapid IHC enhanced marginally the intraoperative diagnosis of the smallest micrometastases, isolated tumor cells (P = 0.06). CONCLUSIONS. Rapid IHC with cytokeratin labeling enhanced the intraoperative diagnosis of SLN metastases in patients with ILC. It may also improve the intraoperative diagnosis of micro metastases.