Table 1.

Immunohistochemistry scoring guidelines for interpretation of Human epidermal growth factor receptor 2 (HER2) protein expression in gastroesophageal junction adenocarcinoma.

Resection specimen staining pattern	Score	Classification
No reactivity or membranous reactivity in <10% of cells	0	Negative
Faint/barely perceptible membranous reactivity in >10% of tumor cells	1+	Negative
Weak/moderate complete or basolateral membranous reactivity in >10% of tumor cells	2+	Equivocal
Moderate/strong complete or basolateral membranous reactivity in >10% of tumor cells	3+	Positive