Cancer is the uncontrolled growth and spread of abnormal body cells. This growth is known as a tumor and can invade and destroy normal tissue. A common place for cancer to occur in males is in the prostate, a walnut-sized gland that provides the fluids necessary for ejaculation. The cause of prostate cancer is not known. What is of major concern is that even when locally advanced, the disease may have no symptoms. That is why many physicians now recommend that all men age forty and older have a yearly rectal exam in addition to PSA testing.