FISH vs. IHC testing accuracy?


Question from Renee: If you had a 2+ staining on the standard HER2 ("IHC") test, but a subsequent 1+ staining on a repeat test using the FISH test, can you really be certain that your HER2 test is negative?
Answers - Ann Ainsworth HER2 testing can be done using a tissue block and staining it with something that is attracted to the HER2 protein. HER2 testing is also performed by another test called FISH. The FISH test looks for the gene itself. The IHC stain is less reliable at the 2+ level than the FISH test. In our laboratory, if the IHC test results are 0 or 1+, the HER2 is considered to be negative. All 2+ and 3+ IHC test results are automatically sent for FISH testing, because this does a better job at that level of IHC staining and is the most reliable test in that circumstance.

A combination of the IHC and the FISH tests are performed in the laboratory to produce the most reliable and accurate results.
Marisa Weiss, M.D. Ultimately, your medical oncologist will depend more on the FISH test for the final answer. The reason why we work so hard to come up with a right answer to the question is it cancer HER2 positive or not is because it can have a significant impact on the choice of treatment.

On Wednesday, November 17, 2004, our Ask-the-Expert Online Conference was called Your Operative and Pathology Reports. Beth Baughman Dupree, M.D., F.A.C.S. and Ann Ainsworth, M.D. answered your questions about details of pathology and operative reports and the importance of discussing them with your doctors.

The materials presented in these conferences do not necessarily reflect the views of Breastcancer.org. A qualified healthcare professional should be consulted before using any therapeutic product or regimen discussed. All readers should verify all information and data before employing any therapies described here.

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