ERBB2 and neoplasm: However, HER2 IHC may be used as a diagnostic marker to assist categorisation if EPC‐like IBC is suspected (an EPC‐like tumour lacks a peripheral MEC layer and shows high nuclear grade features, with or without ER negativity), in which case HER2 positivity (IHC score 3+), would further support a diagnosis of IBC.18, 21, 28, 29