Studies of HER2-positivity rates in GC using immunohistochemistry (IHC) and fluorescence or chromogenic in situ hybridization (FISH/CISH) have shown broad variations, ranging from 6.8% to 34.0 % for IHC,22 7.1% to 42.6% for FISH,22 and 12.2% to 24.0% for CISH.23 This evidence concerns the gene ERBB2 and gastric cancer.