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Table 1 Scoring systems for HER2

From: Confirmation of a low HER2 positivity rate of breast carcinomas - limitations of immunohistochemistry and in situ hybridization

HER2 IHC Scoring
Score Pre-ASCO/CAP Scoring
Interpretation/Staining pattern
ASCO/CAP Scoring
Interpretation/Staining pattern
0 Negative/No staining
Staining in < 10% of tumor cells
Negative/No staining
Staining in <10% of tumor cells
1+ Negative/Faint/barely perceptible
in complete membrane staining
in >10% of tumor cells
Negative/Faint/barely perceptible
in complete membrane staining
in >10% of tumor cells
2+ Weakly positive/Weak to moderate
complete membrane staining
in >10% of tumor cells
Equivocal/Weak to moderate
complete membrane staining
in >10% of tumor cells
3+ Strongly positive/Strong complete
membrane staining
in >10% of tumor cells
Positive/Strong complete
membrane staining
in >30% of tumor cells
HER2 FISH Scoring
Pre-ASCO/CAP Scoring
Interpretation/Ratio (HER2/CEP17)
ASCO/CAP Scoring
Interpretation/Ratio (HER2/CEP17)
Negative/<2.0 Negative/< 1.8
  Equivocal/1.8-2.2
Positive/>= 2.0 Positive/> 2.2
  1. HER2 human epidermal growth factor receptor 2; IHC immunohistochemistry; FISH fluorescence in situ hybridization; ASCO American Society of Clinical Oncology; CAP College of American Pathologists; CEP17 chromosome enumeration probe 17 (probe for the centromer of chromosome 17)