Evaluation of HER2/neu oncoprotein in serum and tissue samples of women with breast cancer: correlation with clinicopathological parameters. 
HER2/neu (HER2) is a proto-oncogen of the EGF Receptor family.  The assessment of serum HER2 level is useful for predicting the patients' response to chemotherapy or hormonal therapy and selection of proper patients for treatment with Herceptin.  We aimed to compare serum HER2 levels with immunohistochemistry in tumoral tissues and investigate correlation between these levels and various prognostic factors.  This cross-sectional study was conducted on 75 patients with breast carcinoma referred to surgical ward of Mashhad Imam Reza's hospital from November 2008 to February 2009.  Pre-operative serum samples were collected and stored in -20°C.  Surgical samples were investigated for the type of carcinoma, tumor size, lymph node metastasis, stage as well as grade of the tumor.  Tissue HER2 over-expression was evaluated by immunohistochemistry (IHC) staining and HER2 levels were studied by ELISA method.  Statistical analysis was performed by SPSS software.  Serum HER2 cut-off level was 18.4 ng/ml; 46.7% of patients were serum HER2-positive and 43% were IHC positive.  There was a high statistical correlation between these two parameters (P=0.018).  Statistically, there was no significant correlation between serum HER2 and age, tumor size, stage, grade and metastatic lymph nodes (P>0.05).  Serum HER2 level assay can be considered as a complementary method besides tissue methods.