Prostate cancer is a malignant tumor that begins in the prostate gland of men. The prostate is a walnut-sized gland located behind the base of the penis, in front of the rectum, and below the bladder. It surrounds the urethra, the tube-like channel that carries urine and semen through the penis. The prostate's main function is to produce seminal fluid, the liquid in semen that protects, supports and helps transport sperm.

Some prostate cancers grow very slowly and may not cause symptoms or problems for years. In this situation, the cause of death is usually not from prostate cancer, but other causes. However, if cancer does metastasize (spread) to other parts of the body, it can cause pain, fatigue and other symptoms. Prostate cancer is somewhat unusual from other types of cancer, in that many tumors that are diagnosed do not spread from the prostate. And often, even metastatic prostate cancer can be successfully treated, with the person surviving in good health for some years.