In prostate cancer, determining the concentration of prostate specific antigen (PSA) alone has displayed limitations in early detection [87].PSA-specific glycosylation changes in serum from prostate cancer patients compared with controls have been characterized by employing matrix-assisted laser desorption/ionization-time-of-flight-mass spectrometry (MALDI-TOF-MS); the levels of α2–3-linked sialic acids on PSA illustrated great potential in discriminating malignant from benign conditions, thereby improving prostate cancer diagnosis [88]. The gene discussed is KLK3; the disease is prostate cancer.