Cytokeratin staining for intraoperative evaluation of sentinel lymph nodes in patients with invasive lobular carcinoma

Background Frozen section and intraoperative imprint cytology (IICN) are 2 methods used for intraoperative pathologic assessment of sentinel lymph nodes (SLNs). The SLN evaluation of patients with invasive lobular carcinoma (ILC) results in a relatively high number of false-negative results using either of these methods. The purpose of this study was to evaluate the added benefits that intraoperative immunohistochemical-cytokeratin staining (ICK-IHC) can bring to IICN in the evaluation of SLN in patients with ILC. Methods A total of 59 breast cancer patients with ILC underwent an SLN biopsy evaluated by our standard IICN assessment in addition to ICK-IHC. The results of IICN with ICK-IHC were compared with the final histopathologic assessment consisting of standard hematoxylin and eosin staining and additional cytokeratin staining of nodes. Results Intraoperative evaluation of SLN using IICN and ICK-IHC correctly diagnosed the nodal status in 45 of 59 (76.3%) patients. On final histopathologic assessment, 31 of 59 (52.5%) patients were found to have positive nodes. Using ICK-IHC, 17 of these 31 positive cases (54.8%) were detected.Using IICN alone, without the benefit of ICK-IHC, only 13 of 31 (41.9%) positive cases were detected intraoperatively. Conclusions For patients with ILC, ICK-IHC staining in addition to IICN improves accuracy over using IICN alone. In this study, ICK-IHC staining demonstrated a 12.9% improvement in the detection of SLN metastases in patients with ILC. Cytopathologists should consider employing ICK-IHC staining to evaluate the touch-imprint slides of SLN in ILC patients