ERBB2 and gastric cancer: Studies of HER2-positivity rates in gastric cancer 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 [7, 8], 7.1 % to 42.6 % for FISH [7, 9], and 12.2 % to 24.0 % for CISH [6].