ERBB2 and invasive breast carcinoma: For over twenty-years HER2 has been assessed in clinical laboratories most commonly using a combined IHC and in situ hybridization (ISH) approach that classifies invasive breast carcinomas as either HER2 positive (3+ and 2+ cases with HER2 gene amplification) or HER2 negative (0, 1+ and 2+ cases without HER2 gene amplification) [1, 3].