A pathologist will look at your biopsy samples under the microscope. If a sample contains cancer it is ‘graded’ to show how active the cancer is. The pathologist looks at the pattern made by the cancer cells and gives that pattern a grade from 1 to 5. This is called Gleason grading.
The pathologist may see more than one grade of cancer, so the grades of the most common pattern and the pattern with the highest grade are added together. This gives your Gleason score.
For Example: If the biopsy samples show that:
Most men with prostate cancer will have a Gleason score between 6 and 10. The higher the Gleason score, the more aggressive the cancer and the more likely it is to spread.