Background: the breast cancer is the second cause of worldwide death. Understanding of molecular pathology of breast cancer can provide useful information about new treatment routes. HER4 gene considered as a molecular pre-prognostic marker in cancers recently. So the purpose of this research is studying of HER4 gene expression in breast cancer patients.

Methods: in this study 70 samples of paraffin blocks of 35 samples from breast cancer patients and 35 normal samples were collected. After slicing and deparaffinization, RNA of samples were extracted and then cDNA synthesis using of M-MuLV enzyme and Oligo dt and Random hexamer primers were done. Statistical analysis of research by Graph Pad prism software with t-test procedure were done.

Findings: results of Real-time PCR show HER4 gene expression decreased in most samples compared to normal ones and It was determined that gene expression has the inverse relation with progression in cancer stage. Therefore, in the samples with first and second stage HER4 gene expression increased 1.11(Pvalue0.048) compared with normal ones and in the third and fourth stage HER4 gene expression 0.624 (Pvalue0.048) decreased.

conclusion: According to the results, the study of HER4 gene expression may have a role as a diagnostic marker in breast cancer. In addition, can be effective in identifying and diagnosing of disease in early stages.