Fully automated HER2 fluorescence in situ hybridisation: successful introduction on a staining platform

The LeicaSelection of therapeutic strategies according to the presence or absence of specific biological markers relies on the availability of accurate and reliable laboratory testing, highlighting the need for standardisation of tissue handling, biomarker assay procedures and accurate interpretation of results. Despite being labour-intensive and technically challenging, fluorescence in situ hybridisation (FISH) assays remain the gold standard for HER2 assessment. Traditionally, HER2 FISH has been performed manually and has lacked a standardised approach, making it subject to inter-laboratory and inter­operator variability. Automation of the staining process addresses a number of challenges associated with HER2 FISH testing, providing a straightforward, labour-saving method to aid standardisation and improve consistency.

HER2 FISH system is a fully automated, quantitative FISH assay for use on the Leica BOND system, employing the PathVysion HER2/CEP17 DNA FISH probes (supplied by Abbott Molecular). The Department of Pathology at the Royal College of Surgeons in Ireland (RCSI) Education and Research Centre has been using Leica’s BOND staining platforms for automation of immunohistochemistry (IHC) staining for five years, and evaluated the performance of the Leica HER2 FISH system compared with its own in-house technique based on the Poseidon ERBB2 probe (Kreatech).

Trial design
A parallel study was performed on a cohort of 100 archived samples of known HER2 protein and/or gene status, comprising: 25 IHC 0/1+ samples, 25 IHC 2+ samples with a FISH ratio <2.0, 25 IHC 2+ samples with a FISH ratio >2.0, and 25 IHC 3+ samples. A mixture of resection specimens and core biopsies was chosen, and all samples were stained in parallel using the laboratory’s in-house technique and the Leica HER2 FISH system. In addition, the same 100 samples were analysed manually by the Heart of England NHS Foundation Trust, Birmingham, using the Abbott PathVysion HER2 DNA probe kit. A total of 20 cells were counted per case using a ratio scoring method, with an additional 20 cells counted in borderline cases (ratios 1.80–2.19).