HER2 testing in gastric cancer: An update

Table 2 Immunohistochemistry scoring for human epidermal growth factor receptor 2 expression in gastric and gastroesophageal junction cancer[17]

Score	Surgical specimen	Biopsy	HER2 overexpression assessment
0	No membranous staining or staining of < 10% of the tumor cells	No membranous staining or staining only in rare cells (less than 5 cohesive cells)	Negative
1+	Staining is weak or detected in only one part of the membrane in ≥ 10% of the cells	Staining is weak or detected in only one part of the membrane of at least 5 cohesive cells	Negative
2+	Moderate/weak complete or basolateral membranous staining in ≥ 10% of the cells	Moderate/weak complete or basolateral membranous staining of at least 5 cohesive cells	Equivocal
3+	Strong complete or basolateral membranous staining in ≥ 10% of the neoplastic cells	Strong complete or basolateral membranous staining of at least 5 cohesive cells	Positive

HER2: Human epidermal growth factor receptor 2.