PSA (prostate-specific antigen) is the most specific tumor marker for prostate cancer and is a serine protease secreted by prostate epithelial cells. Under normal conditions, the PSA-rich prostate alveolar contents are separated from the lymphatic system by a barrier consisting of the endothelial layer, basal cell layer, and basement membrane. When a tumor or other lesion disrupts this barrier, the glandular contents can leak into the lymphatic system and subsequently enter the bloodstream, resulting in an increase in peripheral blood PSA levels. (1) Timing of PSA examination: The Guidelines for the Diagnosis and Treatment of Urological Diseases recommend that men over the age of 50 should receive an annual PSA examination, and for men with a family history of prostate cancer, annual examinations should be performed starting at the age of 45. (2) Determination of PSA results: It is now the more consistent view at home and abroad that a total serum PSA >4.0ng/ml is considered abnormal, and re-testing is recommended for those with abnormal PSA for the first time. When t-PSA is between 4-10ng/ml, the possibility of prostate cancer is more than 25%. When the serum t-PSA is between 4-10ng/ml, the f-PSA level is negatively correlated with the incidence of prostate cancer. The domestic recommendation is f-PSA/t-PSA>0.16 as the normal reference value. Timing of prostate puncture: Prostate puncture should be performed after pelvic MRI and under ultrasound guidance. Indications for prostate puncture: 1 Rectal examination reveals nodules with any PSA value. 2 Ultrasound finding of hypoechoic nodules in the prostate or MRI finding of suspicious signal, any PSA value. 3 PSA >10ng/ml. any f/t PSA. 4 PSA 4-10ng/ml, abnormal f/tPSA If PSA 4-10ng/ml, f/tPSA, imaging is normal, close follow up should be performed.