Determination of her-2/neu by chromogenic in situ hybridization on borderline (2+) immunohistochemistry cases in carcinoma breast.

OBJECTIVE: To determine the HER-2/neu status by chromogenic in situ hybridization (CISH) on tissue specimens with a borderline (2+) immunohistochemistry (IHC) score in carcinoma breast by a descriptive, cross-sectional study in the Histopathology Department, Armed Forces Institute of Pathology (AFIP), Rawalpindi from Jun 2008 to Dec 2009. METHODS: Tissue block specimens from 50 consecutive patients having HER-2/neu score of borderline (2+) on IHC assay were tested for HER-2/neu gene amplification by CISH. Mean and standard deviation were calculated for quantitative variables like age and HER-2/neu gene copy signal/clusters by using SPSS version 14. Frequencies and percentages were also calculated for qualitative variables like type of carcinoma and results of HER-2/neu by CISH (amplified/nonamplified). RESULTS: HER-2/neu gene amplification by CISH was found in 10 (20%) out of 50 patients with borderline (2+) IHC score. All CISH amplified cases belonged to invasive ductal carcinoma type. No significant correlation was noted between type of carcinoma and HER-2/neu gene amplification. CONCLUSION: Chromogenic in situ hybridization (CISH) is a practical, cost-effective and reliable method for analysis of HER-2/neu borderline (2+) cases which may be candidates for Herceptin therapy.