Stages of prostate cancer are divided into A, B, C and D according to the degree of spread. Slower-growing cancer cells take longer to spread, and the grade of the tumor cells—how aggressive they are—is described by the Gleason grading system, which categorizes prostate cell growth and behavior. The Gleason rating, which is between 1 and 10, represents a total score of two parts. One part is given to the predominant cell type and the second part is given to the most aggressive cell type. These two scores are added to become the Gleason rating. Tumors rated 2 to 4 are generally slow growing and are less likely to be life-threatening. Tumors rated 8 to 10 are the more dangerous ones. The majority of patients with localized prostate cancer have Gleason scores 6 to 7.
