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

Table 1 Scoring systems for HER2

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

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)

ISSN: 1746-1596