Since PSA is a tumour-associated antigen (TAA) and not a tumour-specific one, its specificity in prostate cancer diagnosis is not 100%, since inflammation, benign prostate hyperplasia (BPH) or other non-malignant disorders could also cause increased blood PSA levels, while normal PSA levels do not necessarily exclude the presence of a tumour. Here, PROS1 is linked to benign prostatic hyperplasia.