Abstract PS1-04: Utility of rapid- immunohistochemistry using an alternating current electric field for intraoperative diagnosis of sentinel lymph nodes in breast cancer

Axillary lymph node status and pathological diagnosis of sentinel lymph nodes (SLNs) is an important factor that influences management of postoperative therapy. Recent reports indicate that one-step nucleic acid amplification (OSNA) and hematoxylin and eosin (HE)-stained frozen sections are effective for intraoperative diagnosis of SLNs. In the present study, we report a rapid-immunohistochemical staining (R-IHC) method that enables intraoperative detection of SLN metastases within 16 min using an anti-cytokeratin antibody. With this R-IHC system, we apply a high-voltage, low-frequency AC electric field to lymph node sections while they are incubating with the antibodies. The antibodies are mixed within microdroplets and the opportunity for contact between the antibody and antigen is increased. This greatly reduces the time required for the antigen-antibody reaction. This is the report on SLN diagnosis using R-IHC in patients with breast cancer. We prospectively examined 632 dissected SLNs from 260 breast cancer patients who underwent surgery at our institute between July 2014 and March 2020. The dissected SLNs were sectioned and conventionally stained with HE or immunohistochemically labeled with anti-cytokeratin antibody using R-IHC procedures. Intraoperative R-IHC analyses were completed within 16 min, after which diagnoses were made by two pathologists. The total time required for intraoperative diagnosis was about 20 min. In this study, R-IHC detected four metastatic SLNs that were undetected using conventional HE staining (10/52, 19.2%). Compared with subsequent permanent diagnosis, R-IHC offered 98.0% sensitivity, 100% specificity and 99.8% accuracy while those values for intraoperative HE were 80.4%, 100%, 98.4%, respectively (isolated tumor cells were counted as negative). These findings indicate R-IHC is a clinically applicable technique that enables precise, and quick intraoperative detection of micro- and macrometastases in breast cancer. Moreover, R-IHC is cost-effective method: it’s cost is less than a quarter of OSNA and previous report showed that the concentration of primary antibody could be reduced by more than 90% by using R-IHC because AC mixing activated antigen-antibody reaction. Another benefit is its ability to shorten the time needed for microscopic diagnosis itself. When using R-IHC, pathologists are able to readily find metastatic lesions, even within low-power fields (e.g. 40x). This reduces not only the time needed for intraoperative diagnosis, but also the effort necessary to find unclear lesions like small cancer cells (even though it is macrometastasis), micrometastasis, and artifacts of frozen section. This study was conducted at a single institute. Further investigation in a multi-institutional collaborative prospective study will be needed to confirm the utility of this method. But for now, R-IHC appears to be a cost-effective and clinically applicable method for diagnosis of breast cancer and SLN metastasis. Citation Format: Kaori Terata, Hiroshi Nanjo, Eriko Takahashi, Ryuta Nakamura, Yoichi Akagami, Ayuko Yamaguchi, Misako Yatsuyanagi, Chiaki Kudo, Yoshihiro Minamiya. Utility of rapid- immunohistochemistry using an alternating current electric field for intraoperative diagnosis of sentinel lymph nodes in breast cancer [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS1-04.