A prostate cancer diagnosis means cancer cells have formed in the prostate gland. The prostate is a gland below the bladder that makes fluid for semen. Doctors confirm this with a biopsy, removing a small piece of prostate tissue to study under a microscope. Prostate cancer often grows very slowly and may never cause health problems. A person can live a long life with prostate cancer and never know it. But sometimes prostate cancer grows quickly and spreads to other parts of the body. Cancer that spreads this way is considered serious. Doctors may recommend watching the cancer instead of treating it right away. This approach is called observation, and it has two forms. Watchful waiting means having little or no testing unless symptoms appear. If symptoms begin, treatment relieves them, not the cancer itself. Active surveillance means having regular tests to watch for changes in the cancer. If tests show growth, treatment begins to try to cure it. Doctors often choose observation for people whose cancer is unlikely to grow quickly. It is also used when a person has no symptoms or other health conditions. Your care team can help you weigh observation against other treatment choices.