SPP1 and ovarian carcinoma: Among more than fifteen ovarian cancer‐related biomarkers identified to date, the most widely studied include CA‐125, HE4, kallikreins, prostasin (PSN), transthyretin (TTR), transferrin, vascular endothelial growth factor (VEGF), apolipoprotein A‐I (ApoA‐I), and osteopontin (OPN) [42].