Immunohistochemical Biomarkers in Gastric Cancer Research and Management

Table 2

HER2 testing by immunohistochemistry in gastric cancer.

IHC parameters for HER2 testing protocol	IHC score	Classification
Intensity of reactivity
Absent	0	Negative
Faint	1+	Negative
Weak to moderate	2+	Equivocal^*
Moderate to strong	3+	Positive
Degree of membrane reactivity
Complete	2+	Equivocal^*
	3+	Positive
Incomplete	0	Negative
	1+	Negative
Percentage of immunoreactive cells (membrane reactivity)
≥10%	1+	Negative
	2+	Equivocal^*
	3+	Positive
<10%	0	Negative

^* Samples scored IHC 2+ should be retested with fluorescence in situ hybridization (FISH) or chromogenic in situ hybridization (CISH).