In this study we have analysed HER2 amplification in primary breast cancer using a novel, quantitative, dual-colour CISH protocol that converts Texas Red and FITC fluorescent FISH signals to chromogenic red and blue signals, respectively.27 In comparison with previous CISH protocols, this dual-colour CISH protocol features simultaneous determination of HER2 probe signals and chromosome 17 probe signals, thereby eliminating the need for a second round of analysis of chromosome 17 polysomy. The gene discussed is ERBB2; the disease is breast cancer.