[OA-02] Concordance rate of HER2 immunohistochemistry compared to dual-colour in situ hybridisation (DISH) for detecting HER2 amplification in breast cancer
Adiluck Pisutpunya and Kroonpong Iampenkhae
Department of Pathology, Facolty of Medicine, Cholalongkorn University, Bangkok, Thailand
Gold standard of HER2 amplification detection is fluorescence in situ hybridisation (FISH), but it has several limitations. Many centres use dual-colour in situ hybridisation (DISH) assays to detect HER2 gene amplification, which is cost less and can be done in a general laboratory. The aim of this study was to determine concordance between immunohistochemistry (IHC) and DISH testing for HER2 status in breast cancer. A total of 1,307 formalin-fixed paraffin-embedded breast cancer tissues obtained from 2014 to 2021 were evaluated for HER2 score and HER2 gene status using IHC and DISH, respectively. Breast cancer tissues revealed 481 cases of HER2 score 2+ and 826 cases of HER2 score 3+. HER2 gene amplification was detected in 173 (36%) cases of HER2 score 2+ and 760 (92%) cases of HER2 score 3+. There were no amplification of HER2 gene in 308 (64%) cases of HER2 score 2+ and 66 (8%) cases of HER2 score 3+. In conclusion, DISH can be substituted for FISH in the determination of HER2 gene amplification because there is no difference of consistency with HER2 immunohistochemistry.
Keywords: dual-colour in situ hybridisation; gene amplification; HER2 status; immunohistochemistry