Prostate Cancer is the most common cancer in men and PSA is the most important target for management of patients diagnosed with prostate cancer. PSA is a protease exclusively produced in prostate epithelial cells and secreted into the seminal fluid. Moreover, PSA reaches the blood stream and PSA levels have been shown to be proportional to quantity of prostate epithelial cells. Therefore serum analysis has developed the most commonly used method to detect PSA for prostate cancer prevention and to monitor response to therapy. Moreover, PSA immunohistochemistry is an important and common method for routine pathological diagnosis since it allows analysis of cellular expression profiles in prostate cancer.

In diagnostic routine, PSA (HAM18) immunohistochemistry can be used in the following applications

• Carcinoma of unknown origin: Rule out origin from a prostate cancer.
• Bladder tumor of male patients without unequivocal urothelial precursor lesion suggesting urothelial origin: Rule out origin from a prostate cancer.
• Advanced high-grade prostate cancer with rather low serum PSA levels: Low PSA expression in poorly differentiated cancer suggest that serum PSA levels may "underestimate" total tumor mass of the patient.