ERBB2 and neoplasm: First, there were cases that displayed borderline IHC‐2+/‐3+ in terms of intensity; secondly, cases in which the extent of tumour cell staining was around the 10% threshold in cases with heterogeneous staining intensity throughout the tumour (Figure 2); and thirdly, cases that showed staining artefacts such as strong cytoplasmic or nuclear HER2 staining (see Figure S2).