Early detection of breast cancer (BC) is a global target to reduce mortality and morbidity also to improve therapeutic and survival outcomes. Currently, mammography is the gold standard in BC diagnosis followed by biopsy when warranted. Thymidine Kinase 1 (TK1) is a proliferative biomarker that succeeded in discovering premalignant transformations of breast cancer before the appearance of any symptoms. This study aimed to provide a non-invasive method to early detect BC by measuring TK1 in sera of women with breast lesions alongside mammography. The study included 271 women divided into five BIRADS categories. Methods and Material: only one blood sample was collected from each woman to detect TK1 concentration, before undergoing mammography and Fine Needle Aspiration Cytology (FNAC) or true cut. Results: TK1 levels were significantly different between BI-RADS categories. It was correlated with clinical stage, histological grade, lymph node metastasis, and vascular invasion. TK1 levels could distinguish between healthy individuals and patients who had breast lesions with a sensitivity and a specificity as follows 91.3 and 87.5%, respectively. Furthermore, this test could discriminate between benign and malignant breast lesions with a sensitivity of 92.5% and a specificity of 91.2%. Conclusion: These findings suggest the determination of TK1 levels as a risk warning biomarker to improve early detection of BC.