Amplification and Overexpression of HER2/neu Gene and HER2/neu Protein in Salivary Duct Carcinoma of the Parotid Gland

Abstract

OBJECTIVES: To detect amplification of the HER2/neu gene by means of fluorescence in situ hybridization (FISH) in a series of 13 salivary duct carcinomas (SDCs) and to compare the results with immunohistochemical (IHC) assessment of HER2/neu protein expression. DESIGN: Retrospective analysis. SETTING: Department of Pathology, University of Brescia. PATIENTS: We studied 13 cases of SDC diagnosed between January 1, 1997, and June 30, 2004, all arising from the parotid gland. Twelve patients were treated with surgery and radiotherapy, and 1 patient received only palliative radiotherapy. Seven patients died of disease, 3 patients were alive with disease, and 3 were free of disease. MAIN OUTCOME MEASURES: HER2/neu protein expression and HER2/neu gene amplification detected by means of IHC assessment and FISH, respectively. RESULTS: With IHC assessment, 10 cases showed overexpression (grade 3+) of HER2/neu protein, whereas 3 cases were negative for this protein (grade 0/1+). Using FISH, amplification of the HER2/neu gene was found in 8 of the 10 grade 3+ cases, whereas none of the cases negative for the protein according to IHC assessment had amplification of the gene. Because of the small number of patients, it was not possible to statistically correlate HER2/neu protein expression or HER2/neu gene amplification and survival. CONCLUSION: Our data demonstrate that HER2/neu protein is frequently overexpressed in SDC, and in contrast to previous reports, overexpression of the protein is associated in most cases with HER2/neu gene amplification.