Discordant Results Between Immunohistochemistry and Fluorescence in Situ Hybridization

The page below is a sample from the LabCE course HER2 Testing in Breast Cancer. Access the complete course and earn ASCLS P.A.C.E.-approved continuing education credits by subscribing online.

Learn more about HER2 Testing in Breast Cancer (online CE course)
Discordant Results Between Immunohistochemistry and Fluorescence in Situ Hybridization

Discordant results between IHC and FISH are observed in approximately 4% of cases tested. Examples of result discordance are:
  • IHC is 3+, but FISH is negative for amplification
  • IHC <2+, but FISH is positive for amplification
Available clinical data is insufficient in determining whether this discordance represents distinct biologic subgroups or if test results should be considered inaccurate.