Introduction & Objective: Breast cancer is one of the main causes of cancer-related mortality, resulting in approximately 40,000 to 50, 000 deaths annually. Breast cancer is the most prevalent cancer in Iran and in the world, but the epidemiological aspects of Iranian breast cancer is uncertain. Early diagnosis of cancer cells in the peripheral blood is a critical determinant for proper treatment. In spite of the heterogeneity of breast cancer at the molecular level, circulating tumor cells (CTCs) may provide a novel marker. On the other hand, approximately 20-40% of breast cancer patients have shown detectable Cytokeratin 19 (CK19). Materials & Methods: In the present study, the RNA of blood cells of 60 samples (30 patients and 30 normal) was extracted. The RT-PCR technique was applied to the extracted RNA, using specific primers. CK19 expression was evaluated by statistical chi-square test. Results: Cytokeratin-19 was found to be present in the blood of all the patients. However, normal samples were divided in two groups: a) with cytokeratin expression b) without cytokeratin expression. Cytokeratin expression was related with history of cancer in their family. Conclusions: Investigation on the presence of Cytokeratin-19 biomarker in the early stages of disease could be a suitable prognostic factor in blood of the patients. Study on a larger number of patients with more biomarkers with the predictive and/or prognostic value should be considered in the future studies.