ERBB2 and neoplasm: The discrepancy between mRNA level and IHC score that was observed in a few cases could be explained by intratumoral heterogeneity and the ratio of malignant to non‐malignant cells within tumours, which can dilute the influence of the tumour cells on the result, leading to a false‐low mRNA level,39, 50 while a false‐high mRNA level in HER2 score 0 cases was due mainly to the presence of HER2 expression within the in‐situ component.