KLK3 and benign prostatic hyperplasia: Prostate-specific antigen (PSA) is a widely recognized biomarker in PCa detection, but its specificity is limited, especially within the PSA "gray zone" (typically 4-10 ng/mL), where benign conditions, such as benign prostatic hyperplasia (BPH) and prostatitis, can also elevate PSA level [3].