Breast cancer is the most frequent carcinoma in females and the second most common cause of cancer related mortality in women. Early detection of breast cancer is widely reported to be one of the most effective ways leading to better prognosis and lower death rate. For marker discovery, the analysis of mRNA expression signatures in peripheral human blood has been widely used showing to be a promising technique. Cytokeratin-19 (CK 19) is a novel gene that was diagnosed as a highly specific marker for primary breast cancer. The aim of the present study is detecting the expression levels of the CK-19 gene mRNAs in the peripheral blood of breast cancer patients in comparison with benign and healthy controls as a tool for screening and diagnosis the early stage breast cancers, and estimating the diagnostic and prognostic values of these levels in association with tumor size and lymph node status. The marker was determined in peripheral blood (PB) of 55 patients with Invasive Ductal Carcinoma and samples from 20 healthy donors, and 10 women with newly diagnosed benign breast tumors were served as control group using reverse transcriptase polymerase chain reaction (RT-PCR). CK-19 was detected in 41(74.54%) peripheral blood of breast cancer patients while 14(25.46%) patients were CK 19-negative. CK-19 also detected in, 1(10%) of the benign tumors and 2(10%) of healthy individuals. It showed statistically significant relations with size of the tumor, and Lymph node involvement. On the other hand, it was statistically non-significant for age of breast cancer patients. The present study results suggest that CK-19 is a specific molecular marker for detection of breast cancer, discrimination between benign and malignant breast tumors, and it might be of value as a prognostic marker.