The short answer
Grade Group restates the Gleason score on a scale that starts at 1. Grade Group 2 and Grade Group 3 are both Gleason 7, split by which pattern came first, and that order matters.
Grade Group runs 1 to 5, so the lowest prostate cancer grade is 1 rather than a frightening-sounding 6 out of 10.
Grade Group 2 is Gleason 3+4 and Grade Group 3 is Gleason 4+3; the order of the two numbers is the whole difference.
Grade describes how the sampled cells look. It does not say where the cancer is or whether it has spread.
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The full explanation.
The scale was renumbered on purpose
Gleason scores can run from 2 to 10, but in modern practice the lowest one used is 6. So the mildest prostate cancer arrived sounding like 6 out of 10.
At a 2014 meeting of the International Society of Urological Pathology, 65 prostate pathology experts and 17 clinicians from 19 countries took that up directly. They wrote that being told "Gleason score 6 out of 10" implies a middling outlook and adds to a patient's fear of an aggressive cancer.
Their answer was a second scale of five Grade Groups, running 1 to 5. Around 90% of the room backed it. The World Health Organization adopted the term for its 2016 classification.
How the two numbers become one group
A pathologist looks at the tissue and finds the two most common growth patterns. Each gets a number from 3 to 5. Added together, they make the Gleason score.
NCI publishes the conversion, drawn from the AJCC staging manual:
| Grade Group | Gleason score | Gleason patterns |
|---|---|---|
| 1 | 6 or less | 3+3 or less |
| 2 | 7 | 3+4 |
| 3 | 7 | 4+3 |
| 4 | 8 | 4+4, 3+5, or 5+3 |
| 5 | 9 or 10 | 4+5, 5+4, or 5+5 |
The split inside Gleason 7 is the point
Look at rows 2 and 3. Both are Gleason 7. The only difference is which pattern is listed first.
The first number is the pattern the pathologist saw most of. In 3+4, most of the tumor is the tamer pattern 3. In 4+3, most of it is pattern 4.
The 2014 conference singled this out. Grouping every Gleason 7 together, it noted, ignores studies showing a worse outlook for 4+3. Grade Group keeps the two apart, which is why the label is worth reading closely.
What sits behind the numbers
The same conference set out what counts as pattern 4 and pattern 5, so that grading is less a matter of taste:
- Cribriform glands count as pattern 4, whatever else they look like.
- Glomeruloid glands count as pattern 4.
- Small solid cylinders count as pattern 5.
- Clear comedonecrosis, even a little, counts as pattern 5.
- When the look sits on the border between 3 and 4, the lower grade is favored.
The scale was tested before it was adopted, on more than 20,000 prostatectomy specimens and more than 16,000 needle biopsies.
Grade describes tissue, not territory
A Grade Group says how the sampled cells are arranged. It does not say how much cancer there is, which side it is on, or whether it has moved beyond the gland.
NCI states that the Grade Group and the PSA level are both used to stage prostate cancer. Stage also takes in the exam, the imaging, and how much of the gland is involved.
The grade belongs to the tissue that was taken
A needle biopsy samples a few thin cylinders of a walnut-sized gland. What the needle misses cannot be graded.
NCI cites a single-center study of 2,103 men with lesions visible on MRI. Using MRI-targeted cores alone misclassified 8.8% of the cancers defined as significant, compared with doing targeted and systematic cores together.
So it is fair to ask which specimen your Grade Group came from, and how many cores were involved.
Questions worth writing down
- Which Grade Group, and was it 3+4 or 4+3?
- Did this come from a biopsy or from surgery?
- How many cores contained cancer?
- What is my PSA, and what stage does that combination give?
- Does this Grade Group make active surveillance an option?
Related reading
The older scale is explained in What Does a Gleason Score Mean. For the wider picture, see Prostate Cancer, Active Surveillance vs Treatment, and Pathology Reports.
Sources
Words to know
Tap any term to see what it means.
Common questions
Is Grade Group the same as stage?
No. Grade describes how the cells look under the microscope. Stage describes how far the cancer has spread. NCI notes that Grade Group and PSA level are both used to work out the stage.
Why is Grade Group 1 called low grade when Gleason 6 sounds high?
Gleason scores in practice start at 6, so 6 out of 10 sounds mid-range. The 2014 ISUP conference noted this wording added to patients' fear, and renumbered the scale to start at 1.
Can the Grade Group change later?
It can differ between a biopsy and a later surgical specimen, because each looks at different tissue. Ask which specimen your Grade Group came from.
Questions to ask your doctor
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Sources last checked: 2026-07-21 what this meansLast updated: 2026-08-10Next planned review: 2027-07-21
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How this page was created
Cancer Explained does not originate medical claims. Every page restates guidance already published by the National Cancer Institute, the CDC, the USPSTF and the FDA, in plain language, with the source cited so you can check the original yourself. AI does the translating and organizing; automated checks test claims, citations, clarity and safety before anything publishes. We do not employ clinicians and do not intend to — our work is translation and navigation, not clinical judgment. Nothing here is personal medical advice, and no page can account for your particular situation.
Editorial status: Source checked — This page was written with AI assistance and checked line by line against the sources listed on it. That confirms the sources support what the page says. It is not a medical review, and it does not confirm the page is complete or right for your situation.
Human medical review: not completed. Pages here are not signed off by a clinician before they publish. That is not an oversight we are quietly working around: we restate published guidance and cite it, so the authority belongs to the source rather than to us, and every page names where its claims come from — you can verify us instead of trusting us. Where a volunteer clinician has reviewed a page, their name and credentials appear on it; where no name appears, no clinician has checked it. We are glad to have reviewers and are recruiting them, and we do not hold pages back waiting for one. Use this site to understand your situation and to ask better questions of the people treating you.
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