The Gleason score is a system using to grade prostate cancer tissue which is dependent upon how it looks when analyzed under a microscope. The Gleason score ranges from two to ten and is an indicator of how likely it is that the cancer will spread. It also provides the doctor with the necessary information needed to select the most optimal treatment plan for the patient. Similar to staging prostate cancer, grade are given to each prostate cancer case to determine the severity of the disease. A urologist will assign a grade to the prostate cancer after the patient has undergone a prostate biopsy. The tissue samples are sent to a laboratory to be analyzed by a pathologist.