Gleason grading, is the most commonly used system of classifying the aggressiveness of prostate cancer tissue. Based on how it looks under a microscope, a pathologist determines the level of aggressiveness on a scale from 1 to 5. Since more than one level can exist in the same prostate, the two most predominant Gleason grades are added together to give a Gleason score.
- Since Gleason grades range from 1 to 5, Gleason scores will range from 2 to 10. These scores can indicate how quickly the tumor is likely to grow and spread (for example, “3+4=7”).
- When more than one Gleason grade is present, the most predominant grade is written first (“4+3=7” is more aggressive than “3+4=7”)
- Low Gleason score = the cancer tissue is similar to normal prostate tissue and the tumor is less likely to spread.
- High Gleason score = the cancer tissue is very different from normal and the tumor is more likely to spread.