It has been described as an indicator of reduced risk of aggressive disease for doubtful MRI (i.e., Prostate Imaging Reporting & Data System (PI-RADS) 3), or (PSA-D < 0.15 ng/mL) suggestive for a lower likelihood of having clinically significant prostate cancer (csPC) even in case of PI-RADS 3 [33,34,35,36,37,38]. The gene discussed is KLK3; the disease is prostate carcinoma.