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ABSTRACT Background and aim: Breast cancer is the most important malignancy in women, leading to mortality and morbidity in most developed and many developing countries. Considering increasing rate of incidence of breast cancer in Iran molecular investigation seems necessary. In several studies BRCA1 gene mutations had been investigated but in contrast to familial cases, the incidence of non genetic breast cancer is very high. The aim of the present study was to evaluate the role of BRCA1 gene mutations in sporadic cases of breast cancer. Material and Methods: In this study we used PCR-SSCP technique to detect BRCA1 mutations. Thirty paraffin-embedded human breast specimens were reviewed by a pathologist. The specimens had been obtained from the patients with sporadic breast cancer who had been operated in Imam Reza and Taleghani Hospitals in Kermanshah. Tumor samples were studied by use of PCR-SSCP technique to detect mutations in exon 5, exon 11A (300bp) and exon 11B (296bp) of BRCA1 gene. X2 test was used for data analysis. Results: Mutations were detected in 6 cases (20%) 4 cases (13.3%) in exon 5, and 2 cases (6.7%) in exon 11B. No mutation was detected in exon 11A. Conclusion: Our results suggested exon 5 and exon 11B gene mutations contribute to the development of breast cancer in sporadic cases. Key words: Breast cancer, BRCA1 gene, Mutation, Risk factor, Molecular diagnosis. Conflict of Interest: Nill Received: Oct 9, 2008 Accepted: Jan 7, 2010