KLK3 and neoplasm: We classified the tumor serum further into moderately-poorly differentiated clinically significant (GS ≥ 7; PSA 2.0–38.67 ng/mL) and well-differentiated clinically insignificant (GS = 6; PSA 4.1–18.0 ng/mL) tumors, based on the pathological Gleason scoring rendered to the tumors during biopsy.