Wong D, et al. - The concordance of HER2 status between primary and metastatic sites of gastric and gastro-oesophageal junction cancers was determined with the aid of immunohistochemistry (IHC) for protein expression and silver in situ hybridisation (SISH) for gene amplification. There was a high concordance rate of 95%, hus the analysis of primary tumours and metastases was equally valid.