PSA is short for prostate-specific antigen, a tumor marker for prostate cancer, and is commonly used in clinical screening for prostate cancer. PSA is generally found only in the prostate gland, and is produced by secretion of prostate epithelial cells. Under normal circumstances, PSA enters the semen, and only a very low level of PSA enters the bloodstream, and elevated concentration in the blood suggests pathological changes in the prostate. Prostate massage, prostatitis, prostate hyperplasia, and prostate puncture biopsy can all cause elevated PSA levels. It is generally recognized that serum PSA less than 4.0ng/ml is normal, PSA more than 10ng/ml is increased risk of prostate cancer, so the presence of increased PSA, must go to the hospital for a detailed examination to rule out prostate cancer.