SPP1 and breast cancer: The most relevant biomarkers that have occurred in BC include the presence of gene markers such as BReast CAncer Type (BRCA1, BRCA2), and protein-based biomarkers including cancer antigen CA 27.29, carcinoembryonic antigen (CEA), human epidermal growth factor receptor 2 (HER2), vascular endothelial growth factor (VEGF), polypeptide antigen (TPA), cytokeratin 19 fragment (CIFRA-21-1), platelet-derived growth factor (PDGF), and osteopontin (OPN).