Criteria for Her-2/neu immunohistochemical assays
| Interpretation | Microscopic findings |
|---|---|
| Negative | No immunostaining of cytoplasmic membrane identified |
| Negative | Faint or blush staining involving a portion of the circumference of the cytoplasmic membrane in less than 10% of the neoplastic cell population |
| Low positive | Weak but definitive staining of the membrane over 100% of the cytoplasmic circumference in 11–30% of the neoplastic cell population |
| Medium positive | Strong positive staining of the membrane over 100% of the cytoplasmic circumference in 31–50% of the neoplastic cell population |
| High positive | Strong positive staining of the membrane over 100% of the cytoplasmic circumference in 51–100% of the neoplastic cell population |