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Background: Amplification of HER2/neu gene observed in 25–30% of breast cancer patients. FDA approved Trastuzumab is only effective drug used in tumor having the HER2/neu amplification. Fluorescence In Situ Hybridization (FISH) and immunohistochemistry (IHC) are established gold standard techniques widely used to study HER2/neu gene status and their protein expression. Cases with equivocal 2+ using IHC technique showed discordant results with FISH technique. Present study was organized to establish the frequency of HER2/neu gene status by FISH in score 2+ by IHC and to compare these results with clinicopathological parameters in breast carcinoma patients. Methods: Fifty breast cancer patients scored as 2+ by IHC were included in the study. ER and PR status were evaluated for all the enrolled cases. FISH was performed using ZytoLight SPEC HER2/CEN 17 Dual Color Probe Kit. ASCO/CAP (American Society of Clinical Oncology /College of American Pathologists) guidelines were used for analysis. Statistical Analysis (Spearman Correlation, Chi-Square) was done by SPSS software version 23. Results: Out of fifty patients, twenty-eight (56%) were positive for gene amplification while 19 (38%) were negative (ratio ranging from 1 to 10), gene amplification correlated with age, histological grade, and lymph node status. Considerable inverse association obtain between HER2/neu gene amplification and ER (P=0.03, r=-0.3), PR status (P 0.05, r=-0.2). Conclusion: HER2/neu amplification status can reliably determine by FISH especially in equivocal cases by IHC. Accurate assessment of gene with location and their copies in individual cell reveled by FISH. The overall concordance rate between both FISH and IHC results underline the very fact that FISH is gold standard for precise assessment of HER2/neu gene amplification in IHCequivocal breast carcinomas.
