Breast IHC and DISH

Breast biomarkers testing click to access further explanations in the original CAP template

Biomarkers assessments :

- For ER/PR, use Allred scoring for routine service, until further notice.

CAP protocol (June-2021 updated):
ER assessment:	NEGATIVE: < 1%	POSITIVE: >10%; "LOW POSITIVE": 1-10%
PR assessment:	NEGATIVE: < 1%	POSITIVE: >10%

- For HER2, see 2023 ASCO guidelines below.
- Do not report "HER2-Low" or "HER2 Ultra-Low" at this moment
- Reference for 4B5 antibody
- For PD-L1, CPS = Total positive cells / (Positive cells + Negative tumor cells).

- Estrogen recepter (ER) IHC :
	- Intensity :
	- Positive nuclei (%) :
- Progesterone recepter (PR) IHC :
	- Intensity :
	- Positive nuclei (%) :
- Ki67 Proliferation index % :
- HER2/neu oncoprotein IHC : Do not report "HER2-Low" or "HER2 Ultra-Low" at this moment.
	- Score :
	- Cells with Intense Complete Stain (%):
- HER2/neu oncoprotein DISH : HER2 DISH calculator
	- Number of tumor cells counted :
	- Average HER2 signals (black) per cell :
	- Average CEP17 signals (red) per cell :
	- HER2/CEP17 ratio :
	- Cells with Amplified Signals (%):
	- Other ISH abnormalities: Aneusomy Heterogeneous signals
- PD-L1 assessment : - for triple negative tumors PD-L1 calculator
	- Antibody (anti-CD274) :
	- Positive tumor cells (TC% or TPS) :
	- Combined positive score (CPS) :

From Venetis et al Front. Mol. Biosci. 2022.

HER2-low
HER2 IHC 2+ AND HER2 DISH negative
OR
HER2 IHC 1+
Tarantino P et al. 2020

HER2 Ultra-low
It is immunohistochemically characterized by faint/barely perceptible and incomplete staining in =<10% of tumor cells without amplification on FISH.

Analytical details :

- Cold ischemia and fixation times :
- Fixation time in buffered formalin :
- Number of viable tumor cells :

DOWNLOAD THE EXCEL FILE

Dual probe ISH interpretation : - Group 1 = HER2/CEP17 ratio > or = 2.0; > or = 4.0 HER2 signals/cell
- Group 2 = HER2/CEP17 ratio > or = 2.0; < 4.0 HER2 signals/cell
- Group 3 = HER2/CEP17 ratio < 2.0; > or = 6.0 HER2 signals/cell
- Group 4 = HER2/CEP17 ratio < 2.0; > or = 4.0 and < 6.0 HER2 signals/cell
- Group 5 = HER2/CEP17 ratio < 2.0; < 4.0 HER2 signals/cell

Negative : - Group 5;
- Group 4 and concurrent IHC 0-1+ or 2+;
- Group 3 and concurrent IHC 0-1+; and
- Group 2 and concurrent IHC 0-1+ or 2+;

Positive : - Group 1;
- Group 2 and concurrent IHC 3+;
- Group 3 and concurrent IHC 2+ or 3+; and
- Group 4 and concurrent IHC 3+

Comments added in 2023 guidelines:

Patients with breast cancers that are HER2 IHC 3+ or IHC 2+/ISH amplified may be eligible for several therapies that disrupt HER2 signaling pathways.

Invasive breast cancers that test 'HER2-negative' (IHC 0, 1+ or 2+/ISH not-amplified) are more specifically considered 'HER2-negative for protein overexpression/gene amplification' since non-overexpressed levels of the HER2 protein may be present in these cases.

Patients with breast cancers that are HER2 IHC 1+ or IHC 2+/ISH not-amplified may be eligible for a treatment that targets non-amplified/non-overexpressed levels of HER2 expression for cytotoxic drug delivery (IHC 0 results do not result in eligibility currently).”

- Additional notes :