One-day FISH approach for the high-speed determination of HER2 gene copy status in breast carcinoma.

Fluorescence in situ hybridization (FISH) is a commonly used method to detect chromosomal aberrations, for example, to assess human epidermal growth factor receptor 2 (HER2) gene status in breast carcinoma. The classical FISH approach requires overnight incubation for proper hybridization result. Tissue morphologic features are varying because of aggressive pretreatment and application of high temperatures. To eliminate some of the methodological problems, a new 1-day FISH method was recently introduced. The aim of our study was to evaluate the utility of the Instant Quality FISH with the conventional FISH kit from the same provider (Dako pharmDx) for determination of HER2 status. We performed in situ hybridization on the same 40 invasive breast carcinoma samples with both probe kits, and HER2/CEN17 and chromosome 17/cell nucleus ratios were calculated. FISH signal stability was also tested by the reassessment of the slides after 2 months storage. The accordance regarding HER2 gene amplification status between the 2 FISH kits tested was 100%. There was an excellent correlation between HER2/CEN17 ratios with a concordance correlation coefficient of 0.958 and correlation coefficient (R) of 0.959. The 1-day HER2 Instant Quality FISH diagnostic kit points with fast and stable reaction showing the same result in the diagnostic practice when compared with the conventional overnight FISH method.