Comparison of fluorescence in situ hybridization and immunohistochemistry for the evaluation of HER-2/neu in breast cancer

Abstract

Purpose: To compare fluorescence in situ hybridization (FISH) and immunohistochemistry (IHC) in the determination of HER-2/neu status of breast cancers. Materials and Methods: FISH and IHC for HER-2/neu were performed on formalin-fixed paraffin sections of 100 consecutive invasive breast cancers. FISH was performed at Beth Israel Deaconess Medical Center, Boston, MA, using the Oncor/Ventana INFORM kit (Ventana Medical Systems, Tucson, AZ; formerly said by Oncor, Inc, Gaithersburg, MD) in a laboratory certified as proficient in this procedure. IHC was performed at Pheno-Path Laboratories, Seattle, WA, using a polyclonal antibody to the HER-2/neu protein. FISH and IHC were analyzed in a blinded fashion, and the results were then compared. Procedure and interpretation times and reagent costs for FISH and IHC were also compared. Results: HER-2/neu was amplified by FISH in 26% of cases, and 23% were HER-2/neu-positive by IHC. FISH and IHC were both assessable in 90 cases. Concordance between FISH and IHC results was seen in 82 of these cases (91%, P