Gleason Score and Grade Group
If prostate cancer is found when looking at biopsy tissue under a microscope, the pathologist assigns a grade to the cancer. There are 2 grading systems, which can be confusing.
Traditionally, prostate cancer grades were described according to the Gleason Score, a system named for the pathologist who developed it in the 1960s. Dr. Donald Gleason realized that cancerous cells fall into 5 distinct patterns as they change from normal cells to tumor cells. The cells were graded on a scale of 1 to 5. Grade 1 cells resemble normal prostate tissue. Cells closest to 5 are considered “high-grade” and have mutated so much that they barely resemble normal cells.
How is the Gleason Score Derived?
The pathologist looking at the biopsy sample will assign one Gleason grade to the most predominant pattern in your biopsy and a second Gleason grade to the second most predominant pattern. For example: 3 + 4. The two grades will then be added together to determine your Gleason score. Since Dr. Gleason’s original classification, pathologists do not use the lowest Grades 1 and 2. Thus, Gleason scores assigned will range from 6 to 10, with 6 being the lowest grade cancer.
What Does it Mean?
A Gleason score of 6 is low grade, 7 is intermediate grade, and a score of 8 to 10 is high grade cancer. Gleason 7 scores are further divided into 3+4, in which the less-aggressive Grade 3 cells predominate and 4+3, which contain more Grade 4 cells.
It’s also important to know whether any cells rated at Gleason grade 5 are present, even in just a small amount, and most pathologists will report this. Having any Gleason grade 5 in your biopsy samples (or prostate tissue, following surgery) puts you at a higher risk of recurrence.
How Pathologists Consider Gleason Patterns
What is a Grade Group?
In 2014, the International Society of Urological Pathology released supplementary guidance and a revised prostate cancer grading system, called the Grade Groups.
The Grade Group system is simpler, with five grades, 1 through 5.
| Gleason Score | Grade Group |
|---|---|
| Gleason Score 6 | Grade Group 1 |
| Gleason Score 7 (3+4) | Grade Group 2 |
| Gleason Score 7 (4+3) | Grade Group 3 |
| Gleason Score 8 | Grade Group 4 |
| Gleason Score 9-10 | Grade Group 5 |
Many hospitals report both the Gleason score and the Grade Group, but there may be hospitals that still report only the Gleason score.
The grade of your cancer is an important factor in guiding treatment options. For example, many patients with Gleason 6/Grade Group 1 cancers may be appropriate candidates for active surveillance.
Last Reviewed: 12/2023
