_______________________________________________________________________________________________________________________________ Open Access Maced J Med Sci. 2018 Apr 15; 6(4):593-599. 593 ID Design Press, Skopje, Republic of Macedonia Open Access Macedonian Journal of Medical Sciences. 2018 Apr 15; 6(4):593-599. https://doi.org/10.3889/oamjms.2018.124 eISSN: 1857-9655 Basic Science Correlation of Immunohistochemistry and Fluorescence in Situ Hybridization for HER-2 Assessment in Breast Cancer Patients: Single Centre Experience Magdalena Bogdanovska-Todorovska 1* , Slavica Kostadinova-Kunovska 1 , Rubens Jovanovik 1 , Blagica Krsteska 1 , Goran Kondov 2 , Borislav Kondov 2 , Gordana Petrushevska 1 1 Institute of Pathology, Faculty of Medicine, Ss Cyril and Methodius University of Skopje, Skopje, Republic of Macedonia; 2 University Clinic for Thoracic and Vascular Surgery, Clinical Centre “Mother Theresa”, Faculty of Medicine, Ss Cyril and Methodius University of Skopje, Skopje, Republic of Macedonia Citation: Bogdanovska -Todorovska M, Kostadinova- Kunovska S, Jovanovik R, Krsteska B, Kondov G, Kondov B, Petrushevska G. Correlation of Immunohistochemistry and Fluorescence in Situ Hybridization for HER-2 Assessment in Breast Cancer Patients: Single Centre Experience. Open Access Maced J Med Sci. 2018 Apr 15; 6(4):593-599. https://doi.org/10.3889/oamjms.2018.124 Keywords: Breast cancer; HER – 2; Fluorescence in situ hybridisation; Immunohistochemistry *Correspondence: Magdalena Bogdanovska- Todorovska. Institute of Pathology, Faculty of Medicine, Ss Cyril and Methodius University, Skopje, Republic of Macedonia. E-mail: magde_b981@yahoo.com Received: 12-Feb-2018; Revised: 06-Mar-2018; Accepted: 16-Mar-2018; Online first: 23-Mar-2018 Copyright: © 2018 Magdalena Bogdanovska- Todorovska, Slavica Kostadinova-Kunovska, Rubens Jovanovik, Blagica Krsteska, Goran Kondov, Borislav Kondov, Gordana Petrushevska. This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International License (CC BY-NC 4.0) Funding: This research did not receive any financial support Competing Interests: The authors have declared that no competing interests exist Abstract BACKGROUND: Accurate assessment of HER-2 is imperative in selecting patients for targeted therapy. Most commonly used test methods for HER-2 are immunohistochemistry (IHC) and fluorescence in situ hybridisation (FISH). We evaluated the concordance between FISH and IHC for HER-2 in breast cancer samples using Food and Drug Administration approved tests. MATERIAL AND METHODS: Archived paraffin tissue blocks from 73 breast cancer patients were used. HER-2 immunostaining was performed using Ventana anti–HER-2 monoclonal antibody. The FISH assay was performed using PathVysion™ HER-2 DNA Probe Kit. RESULTS: Of the 73 cases 68.5% were IHC 0/1+, 15.07% were IHC 2+ and 16.44% were IHC 3+. Successful hybridisation was achieved in 72 cases. HER-2 FISH amplification was determined in 16.67% cases. Ten IHC 3+ and two IHC 2+ cases were FISH positive. Two of the IHC 3+ cases were FISH negative. Concordance rate was 100%, 18.18% and 83.33% for IHC 0/1+, 2+ and 3+ group, respectively. Total concordance was 84.72%, kappa 0.598 (p < 0.0001). The sensitivity of IHC in detecting IHC 2+ and IHC 3+ cases was 16.7% and 83.3%, and the specificity was 85% and 96.67%, respectively. CONCLUSION: The consistency between the methods was highest for IHC negative and lowest for IHC equivocal cases. The immunohistochemistry showed high sensitivity for IHC 2+/3+ cases and high specificity for IHC 3+ cases. Our results support the view that false-positive rather than false-negative IHC results are a problem with HER-2/IHC testing, and that IHC should be used as an initial screening test, but IHC 2+/ 3+ results should be confirmed by FISH. Introduction The human epidermal growth factor receptor gene HER-2 (also known as HER-2/neu, c – erbB-2) is located on chromosome 17q12 and encodes a member of the epidermal growth factor receptor (EGFR) family with tyrosine kinase activity that is responsible for cell-cell or cell-stroma communication through the process of signal transduction [1]. Activation of the protein receptor is associated with increased cell proliferation, tumour invasiveness, progressive regional and distant metastases, increased angiogenesis and reduced apoptosis [1]. HER-2 gene amplification is the primary mechanism of protein overexpression and is found in nearly 15 to 20% of breast cancer patients [1] [2]. HER-2 gene amplification or protein overexpression are molecular targets for specific targeted therapies associated with good results in early and metastatic HER-2 positive breast carcinomas [3] [4] [5]. Therefore, accurate assessment of HER-2, using reliable, highly sensitive and specific test is imperative in the selection of patients for the therapy [3] [4] [5]. To date, there is still no single, universally accepted test for HER-2 assessment. Two most commonly used techniques are immunohistochemistry (IHC) and in situ hybridisation (fluorescence in situ