PSA and prostate cancer PSA (prostate cancer specific antigen) is a glycoprotein produced by vesicles within the prostate epithelial cell pulp. Under normal conditions, there is a significant barrier between the prostate vesicles and ductal lumen and the blood circulation system, with only trace amounts of PSA in serum and higher levels in semen, which are 100 times higher than those in blood. /When the prostate gland is diseased, the tissue barrier between the prostatic vesicles and the ductal cavity and the blood circulation system is damaged to varying degrees, resulting in leakage of PSA protein into the blood and causing an increase in PSA concentration. The PSA level in the serum is significantly elevated due to the abnormal infiltration of cancerous tissue into the prostate, which causes the PSA to leak into the bloodstream. The amount of PSA in the serum is related to the degree of tissue barrier disruption. PSA has a high sensitivity for the diagnosis of prostate cancer, with a positive rate of 70% and a positive rate of 90% for advanced prostate cancer. It is generally believed that PSA is irreplaceably superior for the diagnosis of prostate cancer, but there are still shortcomings because other diseases of the prostate gland may also show positive findings, so it is not considered to be specific. The final diagnosis still needs to be made on the basis of imaging, anal examination and histology of puncture biopsy. The most important thing is to have a good understanding of the relationship between the two. If the FPSA/TPSA ratio is greater than the threshold value, prostate cancer is less likely, while if it is less than the threshold value, prostate cancer is more likely. The normal value is below 4ng/ml and between 4 and 10ng/ml is the grey area, where prostatitis, prostate enlargement and prostate cancer are possible.