CISH the FISH for HER2: our laboratory experience.

We read with great interest the article by Hoff et al. on the applicability of visualization of fluorescence in situ hybridization (FISH) probes by dual-color chromogenic in situ hybridization (CISH) and totally agree about the need to perform studies on a larger number of samples to confirm their data. In our laboratory, we have been using this technique for 1 year, and to date our sample is composed of 40 cases tested for HER2/centromere 17 status by FISH and subsequent CISH conversion. In our sample, the concordance between FISH and CISH assays is 100%, in complete agreement with the results reported by Hoff et al. As a matter of fact, as we show in the figure, all pairs of ratio values were consistently above or under the cutoff in every case.