Dual color chromogenic in situ hybridization for determination of HER2 status in breast cancer: A large comparative study to current state of the art fluorescence in situ hybridization

Abstract

Background: Chromogenic in situ hybridization (CISH) is fast becoming a well established technique for easy and sensitive determination of HER2 gene status in breast cancer. However, for the chromogenic method to achieve status as a safe and reliable technique, the method needs to be validated against already known and validated FISH techniques. Methods. Here it is reported from a comparative study where HER2 gene status obtained by HER2 CISH pharmDx Kit was compared to HER2 gene status obtained by the FDA approved HER2 FISH pharmDx Kit and the PathVysion HER-2 DNA probe Kit. The study included 365 formalin fixed and paraffin-embedded invasive breast cancer tissue specimens collected consecutively at a US reference laboratory. Results: The data obtained revealed an overall HER2 status concordance of approximately 98% for comparisons of HER2 CISH pharmDx Kit to both HER2 FISH pharmDx Kit and PathVysion HER-2 DNA Probe Kit. Conclusions: The concordance between results obtained using the recently FDA approved HER2 CISH pharmDx Kit with previously FDA approved FISH techniques for HER2 gene status determination indicate that the HER2 CISH pharmDx Kit is a reliable chromogenic alternative to fluorescence-based methods. © 2012 Mollerup et al; licensee BioMed Central Ltd.