Prostate cancer cells, coloured scanning electron micrograph (SEM). The nodular appearance of these cells is typical of cancer cells. The cells may clump to form tumours, which often invade and destroy surrounding tissues. The prostate is a small gland found in men just below the bladder, surrounding the urethra, the tube urine passes through. It produces a fluid that forms part of the semen. Prostate cancer is most prevalent in men over 50 years of age. Treatment is with hormone therapy, chemotherapy, or surgical removal of the prostate. Magnification: x800 when printed at 10 centimetres wide.