KLK3 and prostate cancer: Due to the high heterogeneity of PSA molecular subtypes, elevated levels of serum tPSA are also found in benign prostate diseases.4 An explicit revelation of the PSA subtype proportion during different prostate cancer stages is undoubtedly of great significance.5,6 Clinically, the free to total PSA ratio (% fPSA) in serum is reported to correlate with the severity of prostate disease, but reliable evaluations are challenged by two situations.