ERBB2 and neoplasm: As HER-2 positive status is determined when immunocytochemical staining exceeds a specified threshold (Figure 1(d)), tumours deemed that HER-2 negative may not be wholly negative but do not exceed this “threshold of positivity.” Previous reports by Castiglioni et al. demonstrated that the proportion of Δ16HER-2 expressed was central to malignant transformation [32].