DETECTION OF HER-2 GENE AMPLIFICATION BY CHROMOGENIC IN SITU HYBRIDIZATION (CISH) IN BREAST CANCER : A PRELIMINARY STUDY

HER-2 amplification is an important biomarker and treatment determination in breast cancer. Immunohistochemical (IHC) staining is the accepted method for assessment of overexpression of the protein and dual colour fluorescence in situ hybridization (FISH) is a reliable quantitative assay to carried out precisely HER-2 gene alteration. However, HER-2 FISH method requires specialized fluorescence microscope and their signal definitely fades over time causing it to be impractical for routine laboratories. Chromogenic in situ hybridization (CISH) that uses a simple IHC-like peroxidase reaction is a suitable method and valid option to FISH. The aim of this study is to analyze gene amplification by CISH technique. Fifteen (15) invasive ductal carcinoma (IDC) cases were retrieved from the Pathology Department, Pusat Perubatan Universiti Kebangsaan Malaysia (PPUKM) and scored as 0, 1+, 2+ and 3+ based on IHC overexpression on c-erbB-2 antibody. Four of the total samples demonstrated intermediate expression (2+) followed by assessing HER-2 alteration using Zymed Spot-Light HER2 CISH Kit (84-0146, Zymed Laboratories, CA). All four cases seen under light microscope showed multiple dots and/or large clusters in the majority (>50%) of carcinoma cells. This study showed that these patients with 2+ c-erbB-2 antibody demonstrated CISH-high amplification and this technique is easily conducted as it shown to be practical and can be integrated into routine testing in histopathology laboratory.