Oracle HER2 immunohistochemistry: a biomedical scientist’s view

Testing for human epidermal growth factor receptor 2 (HER2) oncoprotein expression is commonly performed using immunohistochemistry (IHC) techniques to determine which breast cancer patients will or will not respond to treatment with Herceptin (trastuzumab). Many commonly used methods are semi-automated, and introduction of manual steps can lead to high levels of variability and, consequently, unnecessary confirmatory testing by fluorescence in situ hybridisation (FISH).

HER2 testing service
In October 2005, the Department of Health in the UK announced that all newly diagnosed breast cancers would be tested for the HER2 oncoprotein, to assess their suitability for treatment with Herceptin. Immunohistochemistry techniques offer a relatively inexpensive, semi-quantitative assay for the prescreening of tumour samples, with manual fluorescence in situ hybridisation (FISH) or chromogenic in situ hybridisation (CISH) techniques used to provide definitive testing for over-expression of HER2, albeit at a higher cost.

Soon after the 2005 announcement, the cellular pathology laboratory at Salford Royal Hospital in Greater Manchester tendered for, and was awarded, the HER2 testing service for a third of the Manchester and Cheshire hospital network. At this time, the department relied on a semi-automated method using a standardised kit (Dako HercepTest), which, despite regular success in NEQAS evaluations, was not ideal as it required two staff members experienced in IHC to deliver the service.