In prostate cancer, some of the cells within the prostate start to behave abnormally, growing more rapidly and dividing more often. These cells can no longer be considered to be a functional part of the prostate; they have become cancerous. Taken all together, the abnormal cells growing together are called a tumor.
Those cells can stay in place in the prostate, but they can also spread to other parts of the body, and cancerous tumors can grow in other areas.
For most men, however, prostate cancer is a slow-moving disease in which it takes time for the disease to grow and spread. In fact, many men can live a long time without knowing that they have the disease. Because it can be a slow-moving cancer, and because when detected early there are more treatment options with better survival rates, it is important for men to be tested regularly. If testing shows that prostate cancer is present, the chances for survival are much better the earlier the disease is detected, especially if the cancer cells have not spread to other parts of the body. When cancer is caught early, the survival rate can be more than 90%.