Gleason score
When cancer cells are found, the cancer is assigned a grade by the pathologist. The grading system for prostate cancer is called the Gleason score.
This scale uses numbers 1 to 5 to show how much the tissue looks like normal prostate tissue. A grade is given to each of 2 samples of the prostate that have the most cancer cells.
- Grade 1. The tissue looks a lot like normal prostate tissue. The cells are abnormal but still appear to be organized in rings. This may mean a slow-growing cancer.
- Grades 2 to 4. The tissue looks in between normal and very abnormal. The cells vary more in size and shape. Fewer rings are visible. These cancer cells may grow more quickly or may still be slow-growing.
- Grade 5. The tissue looks very abnormal. The cells form irregular, closely packed rings or don't form rings at all. They vary even more in size and shape than lower-grade cells. This grade means it's likely a fast-growing cancer.
The grades from the 2 areas are added together. The main area of cancer gets the first grade score. The second main area of cancer gets the second grade score. That total number is then the Gleason score.
Gleason scores are between 2 and 10. But scores below 6 are seldom used. The results may be reported as:
- Gleason score of 6 or less. This is low-grade cancer.
- Gleason score of 7. This is medium-grade cancer.
- Gleason score of 8 to 10. This is high-grade cancer.
The higher the Gleason score, the more likely the cancer will grow and spread.
Grade groups
Most medical experts use Grade Groups to describe prostate cancer. This is more accurate than the Gleason scores. For example, not all cancers with a Gleason score of 7 are the same. Cancers with more Grade 3 areas (3 + 4 = 7 Gleason score) are less likely to grow and spread than cancers with more Grade 4 areas (4 + 3 = 7 Gleason score). And Gleason score 8 cancers are less likely to grow and spread than cancers with a Gleason score of 9 or 10.
The Grade Group system breaks up prostate cancers into 5 Grade Groups:
- Grade Group 1 = Gleason 6 (or less)
- Grade Group 2 = Gleason 3 + 4 = 7
- Grade Group 3 = Gleason 4 + 3 = 7
- Grade Group 4 = Gleason 8
- Grade Group 5 = Gleason 9 or 10
If your biopsy report shows that you have prostate cancer, it might show both the Gleason score and the Grade Group.