ERBB2 and breast carcinoma: Although BCs have been scored as HER2 0, 1+, 2+ or 3+ by IHC, the numbers of HER2 receptor molecule in human breast cancer cells are continuously distributed, ranging from approximately 20,000 per cell in normal breast epithelium and HER2 IHC 0 BCs to approximately 2,300,000 per cell in HER2 IHC 3+ BCs [49].