A prostate cancer stage defined by the Jewett staging system. Stage A prostate cancer is cancer that began in the prostate and is found in the prostate only. It is usually found during surgery for other reasons, such as benign prostatic hyperplasia (a condition in which an overgrowth of prostate tissue occurs). Stage A is divided into stages A1 and A2. In stage A1, the cancer cells do not look very different from normal cells. In stage A2, the cancer cells look more abnormal or are in several areas in the prostate.