|The prostate is below the bladder and in front of the rectum. The prostate is a gland that makes some of the fluid that is part of semen and found only in males. The size of the prostate grows with age. In younger men, it is about the size of a walnut, however it can be much larger in older men. Just behind the prostate are glands called seminal vesicles that make most of the fluid for semen. The urethra, which is the tube that carries urine and semen out of the body through the penis, goes through the center of the prostate. Prostate cancer is the uncontrolled growth of abnormal cells in the prostate. Cancer develops when the body’s normal control mechanism stops working. Old cells do not die and instead grow out of control, forming new, abnormal cells. These extra cells may form a mass of tissue, called a tumor. Cells in nearly any part of the body can become cancer, and can spread to other areas.