Aims - Chromogenic in situ hybridisation (CISH) is an alternative to IHC or FISH for the assessment of HER2 oncogene status in breast cancer. Although CISH is being used increasingly in routine diagnostics, there are no established inter-laboratory quality assurance programmes for this test. We wished to assess our performance in carrying out and interpreting HER2 CISH when compared to other centres that were also experienced in the assay.
Methods - We assessed the reproducibility of HER2 CISH analysis when performed by seven different centres which use the test routinely in diagnostic service.
Results - The results from 28 cases showed overall concordance of 98.5% (192 / 195 tests) (kappa coefficient 0.91). One of the discrepancies was due to the invasive carcinoma having been cut out in the sections received by two of the centres, and the other two were in the non-amplified / equivocal / low amplified category.
Conclusion - This is the first report of a quality assurance study assessing laboratories that use HER2 CISH routinely in clinical diagnostics. The results show that CISH is a robust technique providing a suitable assay for the frontline testing of HER2 status in breast cancer.