False positivity in break apart fluorescence in-situ hybridization due to polyploidy
Anna Lena van Gulik, Ellen Sluydts, Liesbet Vervoort, Mark Kockx, Pim C. Kortman, Bauke Ylstra, Stephen P. Finn, Lukas Bubendorf, Idris Bahce, Daoud Sie, Teodora Radonic, Birgit I. Lissenberg‐Witte, Erik Thunnissen
Abstract
Background: In-situ hybridization (ISH) is a diagnostic tool in the detection of chromosomal anomalies, which has important implications for diagnosis, classification and prediction of cancer therapy in various diseases. Certain thresholds of number of cells showing an aberrant pattern are commonly used to declare a sample as positive for genomic rearrangements. The phenomenon of polyploidy can be misleading in the interpretation of break apart fluorescence in-situ hybridization (FISH). The aim of this study is to investigate the impact of cell size and ploidy on FISH results. Methods: FISH (lung cancer) signals was manually counted and quantified. Results: FISH result. Conclusions: In case of polyploidy there is an increased likelihood of false positivity when using break apart FISH probes. Therefore, we state that prescribing one single cut-off in FISH is inappropriate. In polyploidy, the currently proposed cut-off should only be used with caution and the result should be confirmed by an additional technique.