HER2/neu estimation by ISH (FISH and CISH) technique in equivocal cases (+2) by IHC in breast cancer

Background: The HER-2/neu oncogene, a member of the epidermal growth factor receptor family, plays a significant role in the development of human breast cancer due to its common amplification. Its detection is paramount for determining the suitability of patients for trastuzumab (Herceptin) therapy and informing treatment decisions involving anthracycline-based and hormonal regimens. The aim of the study is to HER2/neu estimation by ISH (FISH and CISH) technique in equivocal cases (+2) by IHC in breast cancer. Method: Cross-sectional analysis of 52 female breast cancer patients under FISH and 150 under CISH. CISH from Department of pathology/medical city teaching complex/oncology teaching hospital and FISH from AL SHARIQA specialized lab/diagnostic centre from January 2019 to May 2023. Both groups of females were asked their age (years) and FISH or CISH results (positive or negative). Results: Breast cancer patients average 53 ± 11 years. Table 1 shows 38.5% of females aged 50–59 and 30.8% aged 40–49. Only 21.2% of women had HER 2 Neu-positive FISH. 78.8% had HER 2 Neu-negative FISH. FISH for HER 2 Neu is 100% positive in 30-39-year-old women. 30% of women aged 50–59 had HER 2 Neu-positive FISH. 6.3% and 7.7% of women aged 40–49 and ≥ 60 had positive FISH for HER 2 Neu. Breast cancer patients average 50.9 ± 12.2. Table 3 shows 30.7% of women aged 40–49 and 28% aged 50–59. Only 27.3% of women have HER 2 Neu-positive CISH. 72.7% have HER 2 Neu-negative CISH. Age does not affect HER 2 Neu CISH. Conclusion: FISH and CISH showed various age-HER-2/neu oncogene amplification relationships. FISH showed an age-group-HER-2/neu amplification connection, whereas CISH did not. These results emphasise the relevance of the detection technique in interpreting HER-2/neu status in breast cancer and recommend additional study to improve patient classification and therapy decision.