Aims Human epidermal growth factor receptor 2 (HER2)-targeted agents are effective against HER2-positive breast cancers. However, their lack of survival benefit in HER2-negative patients as well as their toxic effects and high cost highlight the need for accurate assessment of HER2 status. Our aim was to evaluate the clinical utility of a reagent-saving in situ hybridisation (Saving ISH) that facilitates hybridisation and saves HER2/chromosome enumeration probe by taking advantage of the non-contact mixing effect of an alternating current (AC) electric field.
Methods With a new device, we apply a high-voltage, low-frequency AC electric field to the tissue sections, which mixes the probe within microdroplets as the voltage is switched on and off. Specimens (n=113) from patients with breast cancers identified immunohistochemically as HER2 0/1(+), (2+) or (3+) were used. The specimens were all tested using conventional dual ISH (DISH), DISH with an automated slide stainer (ASS) and Saving ISH (1:1–1:3 dilution).
Results The Saving ISH with 1:2 probe dilution produced stable results with less non-specific staining while using smaller amounts of probe. The accuracy of HER2 status with Saving ISH was equal to standard. We found 96.4% agreement between DISH using ASS and Saving ISH (kappa coefficient=0.912).
Conclusions These results suggest reagent-saving HER2 ISH could be used as a clinical tool for accurate and stable HER2 assessment, even when reagent concentrations vary.
- breast cancer
- breast pathology
- in situ hybridisation
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Handling editor Runjan Chetty.
Contributors NK collected and analysed the data. KA, YW, KT, AW, YS and SM helped collect the data. KI analysed the data and wrote the paper. HN made pathological diagnoses and supported the research. RN and YA contributed to the development of the device enabling application of a high-voltage, low-frequency AC electric field. YM designed and supervised the research. All authors read and approved the final manuscript.
Funding This work was supported in part by a Grant-in-Aid from the Japan Agency for Medical Research and Development.
Competing interests None declared.
Patient consent for publication Not required.
Ethics approval Institutional Review Board at Akita University Hospital (permit numbers: 1282 and 1408).
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement Data are available upon reasonable request.