Biomarkers are the molecules or tissue based processes that indicate future behavior of the cancer. Broadly classified as tissue-based and blood-based biomarkers, these need special assays over and above the routine clinical, radiological and histopathological examination. Potential of tumor biomarker ranges from risk determination through screening, differential diagnosis, prognosis and prediction to monitoring the disease. Breast cancer is the leading cause of cancer related deaths among women. With progressively better understanding of tumor biology, clinical implications of the molecular behavior are being explored for better therapeutic gains in such patients. Though, to date we have limited range of clinically useful biomarkers in breast cancer; their potential may guide us for cancer therapy in future....