Introduction
- HER2 expression is an important biomarker for the management of RAS wild-type metastatic colorectal carcinoma.
- Immunohistochemistry (IHC) with reflex in situ hybridization (ISH) is accepted as a standard method of assessment, yet there are currently two sets of criteria used to interpret results: HERACLES criteria: ISH confirmation when IHC staining is 3+ in 10-49% of cells.
- My Pathway criteria: Do not require ISH confirmation when IHC staining is 3+ in 10-49% of cells.
- We aimed to assess the prevalence of HER2 3+ heterogeneity and its association with HER2 copy number amplification (CNA).