HER2/neu Status in Breast Cancer Specimens: Comparison of Immunohistochemistry (IHC) and Fluorescence in situ Hybridization (FISH) Methods

Abstract

SUMMARY: HER2 amplification or overexpression is considered as disease outcome and a predictive marker of response to treatment in breast cancer. The present study aimed to compare the results of IHC and FISH for determining HER2 and to search the interpretational differences. Samples (n= 169), of which 31 were the paraffin blocks sent from outer centers, that underwent FISH analysis for HER-2 were included. Samples were re-reviewed by IHC in our laboratory. FISH test was negative in 131 (77.5%) and positive in 38 (22.5%). When those with previous IHC 0-1+ were re-reviewed, the results were found again 0-1+ and none of them was FISH positive. Inconsistency between re-reviewed IHC and previous IHC results was 25% for those with 2+ score and 11% for those with 3+ score. Consistency between IHC and FISH was 17% and 67% for previous IHC 2+ and 3+, respectively, whereas it was 23% and %75 for re-reviewed IHC 2+ and 3+, respectively. Whilst 79% of the samples evaluated as 2+ by the inexperienced pathologist were found to be 0-1+ on the re-review, all of them were FISH negative. According to our results, we suggest that samples with IHC 2+ should be re-reviewed by consulting with an experienced pathologist.

Her-2/neu Oncogene Amplification By Fluorescence In Situ Hybridization And Protein Overexpression On Immunohistochemistry In Breast Cancer

“…8,14,16,19 A Turkish study reported amplification in 75% in IHC 3+ cases which is contrary to the present results. 7 Most of the studies including the present one showed an overall high concordance between IHC3+/FISH amplified and IHC negative/FISH non-amplified groups.…”

“…15,16,20,21 Studies from Turkey, Iran, and Saudi Arabia showed 23%, 27.9% and 23% and gene amplification in cases scoring 2+ immunostaining. 7,14,19 Concordance between IHC scoring 3+ and Her-2/neu gene in Indian studies, 17,18 was 93.9% and 92.9% and discordance of 3.65% and 7.1% between IHC scoring 3+ and Her-2/neu FISH, respectively. Studies from Iran, Taiwan, and Switzerland reported concordance of 81.2%, 83% and 84% and discordance of 18.7%, 16.7% and 16% in cases with IHC staining 3+ and Her-2/neu FISH, respectively.…”

“…Studies from Turkey, Taiwan, India and Iran showed 100% concordance between Her-2/neu negative IHC and FISH similar to the present results. 7,[12][13][14] Studies from Switzerland and USA reported 99%, 95% concordance and 1%, 2% discordance between Her-2/neu FISH and Her-2/neu IHC in cases showing negative immunohistochemistry. 15,16 Other studies from Turkey, India, and Saudi Arabia reported concordance of 80%, 85%, 87% and 84% in cases with negative immunostaining and Her-2/neu FISH, respectively.…”

“…Discordance among the results was attributed to the evaluation process of the samples, staining procedures and both evaluation and staining procedures. 7 Some of the reasons for disparity between IHC 2+ and FISH results included presence of polysomy, intratumoral heterogeneity, variation in fixation, tissue processing, and tumour selection. 8 It could also be due to the different antibodies available in the market for IHC Her-2/neu evaluation.…”

Advances in Nanomaterials-Based Carrier System for the Treatment of Breast Cancer

“…These proteins remain receptors on breast cells. BC patients, the HER2 gene isn't effective suitably [120]. It marks an surplus quantity of copies of itself in a procedure notorious as "HER2 gene amplification."…”