Comparison of immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH) assessment for Her-2 status in breast cancer

BACKGROUND The concordance rate between IHC and FISH according to clinical performance is still controversial. We report a prospective study to reflect the concordance between IHC and FISH in Guilin city, People's Republic of China. METHODS Fifty cases of invasive ductal carcinoma of breast tested by IHC and scored as 0, 1+, 2+ and 3+ by pathologists were further analyzed by FISH using a commercially available double-color probe, and the FISH findings were compared with IHC test results. RESULTS A total concordance of 82.0% was observed with a Kappa coefficient of 0.640 (P<0.001). A high discordance was observed in 30.0% of the patients with IHC 2+, 7.1% in IHC 3+, 19.2% overall in IHC 0 and 1+. CONCLUSION The IHC can be used firstly to screen the HER-2 status, and FISH can be used as a supplementary role to IHC and 2+ and some negative cases. And only those cases with Her-2 status of IHC 3+ or FISH positive should be treated with Herceptin.