ERBB2 and neoplasm: In contrast, according to the updated 2018 guidelines, cases with HER2 IHC2+ and in FISH group 2 are definitively considered as HER2 negative, which is basically dependent on the findings of two retrospective studies (BCIRG-005 for HER2 negative trial and BCIRG-006 for HER2 positive trial) in which there was no HER2 IHC3+ in the subgroup with a HER2/CEP17 ratio ≥2.0 and an average HER2 copy number <4.0 per tumor cell for 35 cases in whom IHC was performed, despite there only being three cases with IHC2+.