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HER2 Testing Accuracy and if HER2 positive definitely needs cheomtherapy

Focus3
Posted by

I have been diagnosed with 9mm grade 3 breast cancer.  ER positive.  Then the IHC HER2 test was boderline 2+ so they did a FISH test whcih has come back positive.  I saw on a website that test results can be different from different labs and the criteria of positive and negative also varying between pathologists is this true?  Also are there any cases with HER2 positive that chemo may not be necessary please?

Thank you

Mandy - Macmillan
Posted by

Hi ,

Thanks for getting in touch.

The two main ways of testing for HER2 are the IHC and the FISH test. If the IHC test comes back 2+ this means it’s borderline and the FISH test is recommended. The FISH test is a more detailed test which will give a positive or negative result based on the amount of HER2 gene in each cell.

IHC and FISH testing is standard across all labs and pathologists shouldn’t be interpreting different results. If you are concerned about the results or the reporting of results, we would recommend discussing this with your consultant or breast care nurse.

Nice guidelines recommend that patients who are diagnosed with a T1c HER2 positive invasive breast cancer are offered trastuzumab (Herceptin) alongside chemotherapy.

I hope this information helps. Please get back in touch if you need to.

Best wishes,

Mandy (Cancer information nurse specialist).