EN2 and Familial prostate cancer: In this study, it has been evidently proven that the 3p3 immunoassay shows superior sensitivity and specificity in the urinary EN2 detection—no false‐negative signals for PCa patients (i.e., 100% sensitivity) and no false‐positive signals for other prostate‐related diseases (BPH and BCa) and healthy controls (i.e., 100% specificity), indicating a precise in vitro diagnosis of prostate cancer.