The short answer
Gleason scores run from 6 to 10 because patterns 1 and 2 are no longer used. Gleason 6 is the lowest grade found in practice, not a middling one, and maps to Grade Group 1.
The Gleason score adds two pattern grades together: the most common pattern first, the second most common next, so 3+4=7 and 4+3=7 are not the same.
Patterns 1 and 2 are rarely used, so the lowest score you will see is 3+3=6. A Gleason 6 is the bottom of the scale, not the middle.
Grade Groups were introduced in 2014 to fix exactly this confusion: Gleason 6 is Grade Group 1, 3+4=7 is Group 2, 4+3=7 is Group 3, 8 is Group 4, and 9-10 is Group 5.
Grade Group 1 is the slowest-growing group; the National Cancer Institute says many men with low-risk prostate cancer may be candidates for active surveillance.
On this page
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The whole article, with every detail and caution.
This page is for men (and their families) reading a prostate biopsy report. It explains Gleason scores, Grade Groups, and why a 6 is the lowest score in use today.
What the Score Measures
The Gleason score describes how prostate cancer cells are arranged when a pathologist examines your tissue under a microscope. It is a grade, not a stage. It says nothing about the size of the tumor or whether it has spread. Areas of cancer are given a pattern number from 1 to 5. Pattern 1 looks close to normal prostate glands. Pattern 5 has lost recognizable gland structure altogether.
Why Two Numbers Are Added
Prostate cancer is usually patchy, with different-looking areas within the same gland. The pathologist grades the two areas that make up most of the cancer and adds them together. That is why your result appears as a sum.
The order matters. In 3+4=7, pattern 3 makes up most of the cancer with some pattern 4 present. In 4+3=7, the more abnormal pattern predominates. Both add to 7, but they are not treated as equivalent.
Why the Lowest Score You Will See Is 6
This is where most of the distress comes from. On paper the scale runs from 2 to 10, so a 6 looks like it sits somewhere in the middle. It does not.
Patterns 1 and 2 are rarely used. That leaves pattern 3 as the lowest in common use, and 3+3=6 as the lowest score you will usually see.
A Gleason 6 is the bottom of the range, not the middle of it. The American Cancer Society says Grade Group 1 (Gleason 6 or less) is the group most likely to grow and spread slowly.
Grade Groups 1 to 5
Because that confusion was so widespread, the International Society of Urological Pathology introduced Grade Groups in 2014. Most reports now list both systems side by side.
- Grade Group 1 — Gleason 6 or lower
- 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
The same cancer that reads as "6" in the old system reads as "1 out of 5" in the new one, which gives a far more accurate impression of where it sits.
What Each Group Broadly Means
- Grade Group 1 is low grade. It is the group most likely to grow and spread slowly. Many men with low-risk disease may be candidates for active surveillance (close monitoring); ask your care team.
- Grade Groups 2 and 3 are intermediate. The split between 3+4 and 4+3 exists because more pattern 4 carries more risk.
- Grade Groups 4 and 5 are high grade and usually lead to more intensive treatment. The higher the Gleason score, the more likely the cancer will grow and spread quickly (NCI).
Grade is only one input. Your overall risk category also draws on:
- your PSA level (a blood test)
- your clinical stage
- other results your team will explain
Why Your Grade Might Change Later
A biopsy samples narrow cores from a small part of the prostate. If the whole gland is later removed and examined, the pathologist sees the full picture and the pathologist may find higher-grade cancer than the biopsy showed (American Cancer Society). This reflects how much tissue was available to look at.
Asking for a Second Read
Gleason grading is expert judgment. If you are unsure about your result, ask your care team whether a second opinion on your pathology makes sense.
Sources
Common questions
My score is 6 out of 10. Isn't that middle of the range?
No, and this is the single most common misreading of a prostate biopsy report. The scale technically runs from 2 to 10, but patterns 1 and 2 are no longer used in routine practice, so 6 is the lowest score you will usually see. The American Cancer Society says almost all prostate cancers are given a grade of 3 or higher; grades 1 and 2 are rarely used. That is why the report also gives a Grade Group, where the same cancer reads as 1 out of 5.
What is the difference between 3+4=7 and 4+3=7?
The first number is the pattern that makes up most of the cancer. In 3+4=7 the lower-grade pattern predominates with some higher-grade pattern present. In 4+3=7 the higher-grade pattern predominates. Both add to 7, but they behave differently, which is why they are separated into Grade Group 2 and Grade Group 3.
Why did my grade change after surgery?
A biopsy takes narrow cores from a small fraction of the prostate. When the whole gland is removed and examined, the pathologist sees everything, and areas of higher-grade cancer that the needle missed may come to light. This is a sampling difference.
Does Grade Group 1 mean I do not need treatment?
It means immediate treatment is often not the only reasonable option. The National Cancer Institute says many men with low-risk prostate cancer may be candidates for active surveillance, which means closely following the cancer and treating only if test results change. Whether it suits you is a decision to make with your care team.
Can Gleason grading be wrong?
Grading is an expert visual judgement. If you are unsure about your result or it would change your decision about surveillance versus treatment, ask your care team whether a second opinion on the pathology makes sense.
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Written by: Cancer ExplainedSources last checked: 2026-07-30 what this meansLast updated: 2026-10-16Next planned review: 2027-07-30
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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, and this 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 then compared with the sources listed on it, looking for statements those sources do not back up. That check is not a sentence-by-sentence record and can miss errors. 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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