Table 2 Predictive markers in breast cancer; thresholds and gray zones requiring confirmation, correlation, and explanation.
From: Prognostic and predictive parameters in breast pathology: a pathologist’s primer
Positive result | Gray zone/borderline result | Negative result | |
IHC nuclear staining: | >10%, strong intensity by IHC | 1–10% or weak staining | <1% or 0% |
Correlation with histology recommended | |||
Confirmation: | No additional confirmation | Lab-specific SOP to confirm or adjudicate results | Lab-specific SOP to confirm or adjudicate results |
Explanation/reporting: | Report positive results | Report as Low Positive with recommended comment about uncertainty of results close to thresholds | Report negative results, along with status of controls |
Positive result | Gray zone/borderline result | Negative result | |
IHC membranous staining: | 3+ by IHC | 2+ by IHC | 0–1+ by IHC |
Correlation with histology recommended | |||
Confirmation: | No additional confirmation | In situ hybridization (ISH) as reflex test | No additional confirmation |
Explanation/reporting: | Report as positive | Equivocal, defer to ISH testing | Report as negative |
In situ hybridization testing (ISH), dual probe: | Group 1 by ISH | Groups 2–4 by ISH | Group 5 by ISH |
Correlation with histology recommended | |||
Confirmation: | No additional confirmation | Review concurrent IHC from same sample. If 2+ by IHC second observer recounts ISH. | No additional confirmation |
Explanation/reporting: | Report as positive | Report as overall HER2 positive or negative based on combined results of IHC and ISH (per guidelines). Use recommended reporting comments to clarify limited data on these groups. | Report as negative |
