OBJECTIVETo evaluate the application of the immunohistochemistry (IHC) and the fluorescence in situ hybridization (FISH) in detecting the amplification and the expression of HER-2 gene in the breast cancer patients.

METHODSSixty-six cases of paraffin-embeded breast cancer samples with overexpression, low or no expression of HER-2 gene as detected by IHC were analyzed for HER-2 gene amplification using FISH.

RESULTSAmong the 42 samples with HER-2 gene overexpression (3+/2+) detected by IHC, 31 showed positive HER-2 gene amplification and 11 showed negative HER-2 gene amplification in FISH. In the 24 samples with low or no HER-2 gene expression (1+/-) detected by IHC, no HER-2 gene amplification was detected by FISH. The results of the two testing methods showed a good consistency with the kappa coefficient of 0.672 (P<0.001). We also found that the 17 chromosome polysomy in 42% of the samples and the incidence of 17 polysomy was significantly higher in the HER-2 gene overexpression (3+/2+) group than in low or no HER-2 gene expression (1+/-) group (chi(2)=4.688, P=0.03).

CONCLUSIONIHC can be used as a screening method for detecting HER-2 gene amplification, and FISH should be performed in cases of HER-2 gene overexpression (3+/2+) as detected by IHC.