ERBB2 and invasive carcinoma: The most widely used methods at present are IHC, FISH and CISH due to their propensity in evaluating HER2 in FFPE tissues in invasive carcinoma.31 Most HER2 studies have been performed by IHC, which is widely accessible, easy to perform at a reasonable cost and is appropriate for initial HER2 assessment.32 However, in cases with an IHC score of 2+, the inter-observer agreement is poor, and the predictive value is unsatisfactory for clinical use.