Carcinoma of the prostate arise from

(Peripheral zone) (1045-CSDT 12th) (1354-B &L 25th)CARCINOMA OF PROSTATE - 90% of tumours are adenocarcinoma the tumour arises primarily in the peripheral zone (70%) an area that differs in embryoic derivation from the periurethral (transition) zone which is the site of formation of benign prostatic hyperplasiaScreening - by transrectal ultrasound (TRUS/and prostate specific antigen (PSA)* PSA = (under age 55 years) normal > 2.5 ng/ml= over age 65 years/ normal > 6.5 ng/ml.* PSA density (PSA divided by prostate volume) >0.15 suggest cancer* Percent free PSA (Total PSA minus complexed PSA) where when < 10% the risk of prostate cancer is 60% (only useful with total PSA 2-10 mg/ml)* Newer methods for measuring unbound (free) PSA have substantial promise for differentiating benign from malignant disease