What causes discordant results in HER2 tests of breast tumors?

Updated: Mar 20, 2019
  • Author: Oudai Hassan, MD; Chief Editor: Chandandeep Nagi, MD  more...
  • Print
Answer

Answer

Discordant results

Discordant results (IHC 3+ with negative FISH result or IHC < 3+ with positive FISH result) are found in approximately 4% of patients. The available clinical data are insufficient to determine whether these represent distinct biologic subgroups with therapeutic implications or whether they are inaccurate test results.

HER2 overexpression does not equal benefit from anti-HER2 therapy. Some patients exist who truly overexpress HER2 but have upstream or downstream anomalies that render the interaction with trastuzumab ineffective.

Quantitative image analysis is encouraged by ASCO/CAP for cases with weak membrane staining 1-2+ to improve the consistency of interpretation.


Did this answer your question?
Additional feedback? (Optional)
Thank you for your feedback!