The human epidermal growth factor receptor-2 (HER2) gene plays a critical role in breast cancer development and progression. HER2 overexpression characterizes a biologically and clinically aggressive breast cancer subtype. In this study, 60 samples from Iraqi women with breast cancer were collected and investigated for HER2 protein in the tissue by immunohistochemistry. Also, 20 samples from healthy Iraqi women were used as a control. The results showed that 18 (30 %) patients expressed the HER2 protein. A molecular study for single nucleotide polymorphism (SNP) was conducted on samples metastasizing to lymph nodes. DNA was extracted and polymerase chain reaction (PCR) was performed to amplify exon 17 and intron 17 of HER2 gene. Sequencing of PCR product was achieved and two SNPs of HER2 gene, one in exon 17 (Ile655Val) and another close to it in intron 17 (rs903506) were studied. In exon 17, SNP Ile655Val was found in 41% of patients, while in intron 17, the non-coding SNP rs903506 was found in 27% of patients. However, no polymorphism was found in the control group. The results may suggest that HER2 gene can be used as a molecular marker for breast cancer.
