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A new perspective on HER2 testing
Evolving lab practices to match clinical advances
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Speaker: Prof. Dr Abeer Shaaban MBBCh, MSc, PhD, FRCPath
5th June 2024
This non-promotional event was organized and funded by AstraZeneca and is intended for healthcare professionals only. Z4-65702. DOP: June 2024. These questions were answered by Prof. Dr Shaaban during the Q&A session of this Lab Talk. The answers reflect her professional view and expertise and do not reflect the views of AstraZeneca. This content is for educational purposes only. AstraZeneca does not guarantee that the suggestions and methods implemented here will work for your institution. Not for further distribution.
Q1: Does the pilot NEQAS scheme include FISH or is it only HER2 IHC?
It’s only IHC at the moment, but NEQAS have a separate HER2 FISH scheme. This is particularly done for HER2 low, to make sure that we as labs stain it correctly and interpret correctly.
Q2: Does the pilot NEQAS scheme include FISH or is it only HER2 IHC?
For HER2 low by definition, you probably won’t see much at 5x or 10x.
Try to assess, go low power first and see if you can see any staining or not. If you cannot see any at 5x, this is not strong. Go to 10x and see if you can get any staining. If you can see some staining there, then there is a little bit at least of a moderate staining. Then go higher and assess the rest. The idea is to see the proportion of cells that will have complete or incomplete staining and take it from there. Generally, if you have complete staining around 10%, you’re in the 2+ category, again it could be HER2 low at the end. So, go from very low power to high power and assess the percentage and completeness and try to categorize it.
Q3: What would you highlight as the key pre-analytical variable to optimize HER2 testing, especially regarding low levels of expression?
Q4: What do you think are the key aspects to include in the reporting? For example, descriptive terminology, considering the end user and the clinical context.
A comment on what it means for the clinician is useful. For example, when you have heterogeneity, what’s the type of heterogeneity? This will need discussion. For FISH, you would comment on each heterogeneous area separately and discuss in the MDT. It is not as black or white and in some difficult cases discussion is required with the clinical team, particularly in the heterogeneous category. So, nothing has changed from what we do now, but if you want to add to it a comment on the HER2 low category, you can do that. from there. Generally, if you have complete staining around 10%, you’re in the 2+ category, again it could be HER2 low at the end. So, go from very low power to high power and assess the percentage and completeness and try to categorize it.
Q5: What would you say are the key technical points to consider when it comes to FISH to ensure accurate analysis and reporting?
Q6: How to minimize variability in immunohistochemical analysis results in these cases depending on the antibody clone used?
The most commonly used antibodies generally in the EU are the VENTANA and the Dako HercepTest. The studies that have been done so far have shown that there is a difference, so depending on the antibodies you use the results will not be identical and that’s something to keep in mind. There are some studies that have shown that Ventana 4B5 picks up a lot more of the HER2 low category than Dako, but Dako now have got their monoclonal test that they project is picking a lot more than before. It’s important to identify which one you’re using and recognize that means they will not be the same. I think the Ventana 4B5 is the most commonly used and it is FDA approved. In the UK, that’s the most used antibody as well. However, if you’re using another one, it’s not a problem, just make sure that it works well, the quality assurance is good and that you participate in the relevant quality assurance scheme.
Q7: What is your approach to borderline or complex cases in HER2 expression, do you get a second opinion?