KLK3 and Familial prostate cancer: Prostate cancer (PCa) is the second most common solid tumor in men and the fifth cause of cancer mortality,[1] with an estimate of 288,300 new cases and 34,700 deaths in the United States in 2023.[2] Currently, the cornerstones of PCa management include serum prostate-specific antigen (PSA) quantification, digital rectal examination, and systemic transrectal ultrasound-guided biopsies.[3] Molecular biomarkers supplement existing clinicopathologic tools for PCa diagnosis and prognosis by providing additional and valuable information about the biological behavior of PCa.