Correlation between HER2 gene amplification and protein overexpression through fluorescence in situ hybridization and immunohistochemistry in breast carcinoma patients

Background : In India, the incidence of breast cancer has increased in the urban population, with 1 in every 22 women diagnosed with breast cancer. It is important to know the HER2/neu gene status for a better prognostication of these patients. Aim : The aim of this study was to compare the efficacy of fluorescence in situ hybridization (FISH) and immunohistochemistry (IHC) for determining HER2/neu alteration in breast carcinoma. Materials and Methods : A total of 188 histologically proven breast carcinoma cases between the years 2007 and 2011 were retrospectively analyzed on the paraffin tissue sections by both IHC and FISH techniques. FISH for HER2/neu gene amplification was performed on cases where the IHC status was already known and the results were compared. Results : A total of 64 (30%) patients were found to be amplified and the remaining 124 (65.9%) cases were found to be unamplified through FISH. Patients observed with 3+ reading on IHC were later confirmed as unamplified in 29.5% cases through FISH. Conclusion : It has been confirmed with the present study that IHC is a prudent first-step technique to screen tissue samples for HER2/neu gene status, but should be supplemented with the FISH technique especially in equivocal cases.