Gleason score
Meaning of Gleason score: Two numbers added together, one for the commonest growth pattern and one for the next, describing how far prostate cancer has strayed from normal.
Definition of Gleason score
The Gleason score measures how abnormal prostate cancer tissue looks under a microscope. A pathologist assigns a pattern number to the most common architecture in the sample and a second number to the next most prominent pattern, then adds the two. Higher totals mean the glands are less organized and the cancer is more likely to grow quickly and spread.
How is the number worked out?
The grading looks at architecture rather than at individual cells: how well the tissue still forms separate, rounded glands. Patterns run from 1, which is almost normal, to 5, in which glands have disappeared and sheets or cords of cells remain. In current practice only patterns 3, 4 and 5 are assigned to cancer on a biopsy, so the lowest total reported is 6. Two numbers are given because a tumor is rarely uniform, and their order carries information: 3+4 means mostly pattern 3 with some pattern 4, while 4+3 means the reverse and carries a worse outlook.
What do the totals mean?
| Gleason score | Grade Group | What it indicates |
|---|---|---|
| 6 | 1 | Lowest grade reported, glands still well formed |
| 3+4=7 | 2 | Mostly well formed with a minor poorly formed component |
| 4+3=7 | 3 | Mostly poorly formed |
| 8 | 4 | Poorly formed throughout |
| 9 or 10 | 5 | Little or no gland formation |
Why was the Grade Group scale added?
The original scale ran from 2 to 10, so a score of 6 sounds like a middle result when it is in fact the least aggressive cancer that gets reported. That mismatch pushed people toward treatment they might not have needed. The Grade Group scale, running from 1 to 5, restates the same information so that the mildest disease is called group 1. Reports now usually carry both.
What does it not tell?
Grade is not stage. The score describes how the tissue looks, not how far the disease has traveled, and a microscope cannot show whether the tumor has reached beyond the gland. Risk is judged by combining the grade with the PSA blood level, the extent found on examination and imaging, and how much of the sampled tissue is involved. A score from a needle biopsy can also differ from the score assigned after the whole gland is removed, because the biopsy samples only part of an uneven tumor. This is one reason prostate cancer reports are reviewed as a whole.
Also known as
Used in a sentence
The biopsy showed adenocarcinoma with a Gleason score of 3+4=7, corresponding to Grade Group 2.
Good to know
A Gleason score of 6 is the lowest grade reported in current practice rather than a middle value, which is why the Grade Group scale from 1 to 5 is given alongside it; the order of the two numbers also matters, since 4+3 carries more risk than 3+4.