HER-2/neu gene amplification in carcinoma ex pleomorphic adenoma in relation to progression and prognosis: a chromogenic in-situ hybridization study

Aims: The aim of this study was to investigate the potential role of HER-2/neu in the stepwise progression of carcinoma ex pleomorphic adenoma (CXPA) and to evaluate its prognostic significance in CXPA. Methods and results: We examined HER2 overexpression and HER2 amplification by immunohistochemistry and chromogenic in-situ hybridization in 31 cases of CXPA with ductal differentiation (eight intraductal, five intracapsular, and 18 extracapsular) and seven cases of atypical pleomorphic adenoma (PA). HER2 overexpression and HER2 amplification were found in 17 (54.8%) and 12 (38.7%) of the 31 CXPA cases, respectively. HER2 amplification was more prevalent in extracapsular CXPAs (9/18 cases; 50%) than intracapsular CXPAs (1/5 cases; 20%), intraductal CXPAs (2/8 cases; 25%), or atypical PAs (0/7 case; 0%). The status of HER2 amplification was essentially retained from the intraductal to the extracapsular component in individual extracapsular CXPAs. In addition, HER2 amplification was significantly associated with a worse prognosis (shorter disease-free survival time and shorter overall survival time) among extracapsular CXPAs (each P < 0.05). Conclusions: These results suggest that HER2 may play an important role in the progression of CXPA, and that HER2 amplification may be an additional prognostic indicator of CXPA.