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. 2019 Mar 19;19(1):1–48. doi: 10.5230/jgc.2019.19.e8

Table 4. Interpretation of IHC findings [244,245].

HER2 status Intensity IHC staining
Negative 0 Reactivity in <10%* of tumor cells
Negative 1+ Faint membranous reactivity in ≥10% of tumor cells; reactive only in part of their membrane
Equivocal 2+ Weak to moderate complete or basolateral membranous reactivity in ≥10% of tumor cells
Positive 3+ Strong complete or basolateral membranous reactivity in ≥10% of tumor cells

IHC = immunohistochemistry; HER2 = human epidermal growth factor receptor 2.

*For biopsy samples, measure scores when stained tumor cell clusters (≥5 cells) are present, irrespective of the percentage of tumor cells; Only membranous staining should be considered true reactivity.

HHS Vulnerability Disclosure