Gleason Scores and Grade Groups in Prostate Cancer Explained
Author: Ian C. Langtree - View Credentials
Published: 26 Jan 2025 - Updated: 27 Oct 2026
Publication Type: Informative
Table of Contents:
Synopsis - Definition - Overview - FAQs - Insights, Updates - Related Content
Synopsis
This information explains how pathologists grade prostate cancer using the Gleason score and the newer Grade Group system, which sorts scores of 6 through 10 into five simpler categories now endorsed by the International Society of Urological Pathology and the World Health Organization. It is written for men waiting on or reviewing biopsy results, including older men and those managing other health conditions, and it shows why the numbers matter, since a Gleason 7 recorded as 3+4 or 4+3 can point toward quite different outlooks and treatment paths. A side-by-side chart pairs each score and Grade Group with its cell appearance, aggressiveness, risk of spread, and typical treatment considerations, while a separate section shows how PI-RADS imaging, biopsy, and PSA testing fit around the grade, giving patients and families plain-language grounding for informed conversations with their care team.
At a Glance
- 1 - A Gleason 8 can be made up of 4+4, 3+5, or 5+3, and all three combinations fall into Grade Group 4.
- 2 - Gleason patterns 1 and 2 are rarely assigned on modern biopsies, so 6 is effectively the lowest score reported today.
- 3 - Grade Group 1 was introduced partly because a score of 6 sounded like mid-range cancer on an old 2 to 10 scale, alarming many men with slow-growing disease.
- 4 - High-grade cancers are usually treated with radiation plus long-term hormone therapy or with surgery, while chemotherapy is mainly reserved for cancer that has spread.
Topic Definition
- Gleason Score
A Gleason score is the standard pathology grade for prostate cancer, describing how abnormal the cancer cells look under a microscope and therefore how aggressively the tumor is likely to behave. A pathologist rates the most common and second most common cell patterns in the tissue on a scale of 1 to 5 and adds them together, producing totals that in current practice run from 6 to 10. Since 2014 these totals have also been reported as Grade Groups 1 through 5, a simpler scale that separates 3+4 from 4+3 and places the lowest-risk cancers at the bottom where patients expect them. Lower scores and Grade Groups point to slow-growing disease that may only need monitoring, while higher ones signal cancer more likely to grow and spread, so the grade is weighed alongside stage, PSA level, and overall health when treatment is planned.
Overview
Prostate cancer is one of the most common cancers among men, and its diagnosis often involves a Gleason score, which plays a crucial role in determining the aggressiveness of the cancer and guiding treatment decisions. The Gleason score is derived from the Gleason grading system, a method used by pathologists to evaluate the pattern of cancer cells in prostate tissue samples. Understanding this score can help patients and healthcare providers make informed decisions about the course of treatment.
What is the Gleason Score?
The Gleason score is a numerical value used to describe the aggressiveness of prostate cancer based on the pattern and appearance of cancerous cells when viewed under a microscope. The score is made up of two components:
- Primary grade: The most common pattern seen in the biopsy sample.
- Secondary grade: The second most common pattern observed.
Each grade is assigned a number between 1 and 5, with 1 representing the least aggressive cells and 5 representing the most aggressive. The two grades are then added together to form the Gleason score. For example, if the primary grade is 3 and the secondary grade is 4, the Gleason score would be 7 (3+4).
Gleason Score and Cancer Aggressiveness
The Gleason score provides information about how likely the cancer is to spread (metastasize). Higher scores indicate more aggressive cancers, which are more likely to grow and spread quickly. On the other hand, lower scores generally suggest that the cancer is less aggressive and may grow more slowly.
What Are Grade Groups?
In 2014 the International Society of Urological Pathology agreed on a simpler way to report prostate cancer grade, and the World Health Organization adopted it in 2016. Called the Grade Group system, it sorts Gleason scores into five groups numbered 1 to 5, and most pathology reports now list both the Gleason score and the Grade Group.
The change fixed two long-standing problems. First, Gleason patterns 1 and 2 are rarely assigned on modern biopsies, so 6 became the lowest score in practice - yet on a scale that appeared to run from 2 to 10, a 6 sounded like middle-of-the-road cancer to many men. Calling it Grade Group 1 places it correctly at the bottom of the scale. The lowest-risk group is the subject of ongoing debate, covered in Should Low-Grade Prostate Abnormalities Be Classed as Cancer? Second, Gleason 7 was treated as one category even though 3+4 and 4+3 behave differently. In a 3+4 cancer the lower-grade pattern 3 cells are most common, while in a 4+3 cancer the more aggressive pattern 4 cells dominate, so the two are now separated into Grade Groups 2 and 3.
- Grade Group 1: Gleason 6 (3+3) or lower
- Grade Group 2: Gleason 7 (3+4)
- Grade Group 3: Gleason 7 (4+3)
- Grade Group 4: Gleason 8 (4+4, 3+5, or 5+3)
- Grade Group 5: Gleason 9 or 10 (4+5, 5+4, or 5+5)
Large studies of men treated for prostate cancer found that each step up the Grade Group scale was linked to a clearly higher chance of the cancer returning after treatment, which is why the five groups are now used alongside PSA level and cancer stage when doctors assign an overall risk category.
Breakdown of Gleason Scores
| Gleason Score | Grade Group | Description | Aggressiveness | Risk of Metastasis | Treatment Considerations |
|---|---|---|---|---|---|
| 6 (3+3) | 1 | Well-differentiated cancer (low grade) | Low | Very Low | Active surveillance is usually preferred; surgery or radiation in selected cases. |
| 7 (3+4) | 2 | Moderately differentiated cancer, mostly pattern 3 | Moderate | Low to Intermediate | Surgery or radiation; active surveillance may suit some men with a small amount of pattern 4. |
| 7 (4+3) | 3 | Moderately to poorly differentiated cancer, mostly pattern 4 | Moderate to High | Intermediate | Surgery, or radiation often combined with short-term hormone therapy. |
| 8 (4+4, 3+5, or 5+3) | 4 | Poorly differentiated cancer | High | High | Surgery, or radiation combined with long-term hormone therapy. |
| 9 (4+5 or 5+4) | 5 | Very poorly differentiated cancer | Very High | Very High | Radiation with long-term hormone therapy, or surgery as part of multimodal care; chemotherapy is mainly used if the cancer has spread. |
| 10 (5+5) | 5 | Undifferentiated cancer (high grade) | Very High | Very High | Multimodal treatment as for Gleason 9, with clinical trials often considered. |
Detailed Explanation of Gleason Score Ranges
Gleason Score 6 (3+3) - Grade Group 1:
The cancer cells in this category resemble normal cells and grow slowly. This is considered a low-grade cancer and is less likely to spread. Treatment options may include active surveillance or surgery, depending on the patient's overall health and preferences.
Dropping the Cancer Label May Cut Prostate Deaths: A UCLA-led model finds relabeling the lowest-risk prostate cancer could cut overtreatment and prevent nearly 2,400 deaths a year through more screening.
Gleason Score 7 (3+4 or 4+3) - Grade Groups 2 and 3:
This score indicates moderately differentiated cancer, where cells look more abnormal and may grow more quickly than low-grade cancers. Gleason 7 cancers are considered intermediate in terms of aggressiveness and risk of metastasis. Treatment often includes surgery, radiation, or active surveillance, based on other factors such as age and overall health.
A 3+4 cancer (Grade Group 2) generally has a better outlook than a 4+3 cancer (Grade Group 3), because the less aggressive pattern makes up most of the tumor. Some men with Grade Group 2 disease and only a small amount of pattern 4 may be candidates for active surveillance, while Grade Group 3 is usually treated.
Gleason Score 8 (4+4, 3+5, or 5+3) - Grade Group 4:
At this level, the cancer is more likely to spread to surrounding tissues and organs. Gleason 8 cancers require aggressive treatment, such as surgery or radiation therapy, and may be accompanied by hormone therapy. The prognosis depends on other factors, including the patient's general health.
Gleason Score 9 (4+5 or 5+4) - Grade Group 5:
This represents highly aggressive cancer that is likely to grow and spread quickly. Treatment typically involves radiation combined with long-term hormone therapy, or surgery that may be followed by radiation. Chemotherapy is generally added when the cancer has spread or stops responding to hormone therapy. The prognosis depends on the extent of spread and response to treatment.
Gleason Score 10 (5+5) - Grade Group 5:
Gleason 10 cancers are the most aggressive form of prostate cancer. The cancer cells are undifferentiated, meaning they bear little or no resemblance to normal prostate tissue. The likelihood of metastasis is very high, and treatment is intensive, often combining radiation and long-term hormone therapy or surgery, with chemotherapy and clinical trials considered, particularly if the cancer has spread. The outlook can vary, depending on how well the cancer responds to treatment.
Difference Between Gleason Score and PI-RADS
The Gleason Score and the Prostate Imaging Reporting and Data System (PI-RADS) are both used in the context of prostate cancer, but they serve different purposes and assess different aspects of the disease. The Gleason score is a post-diagnosis grading system that evaluates cancer aggressiveness, while PI-RADS is a pre-diagnosis imaging-based scoring system that helps assess the likelihood of cancer.
PI-RADS is a standardized scoring system used to assess the likelihood of prostate cancer being present based on prostate MRI images. It helps radiologists and clinicians identify areas within the prostate that may require biopsy. The PI-RADS system grades prostate lesions on a scale of 1 to 5 based on MRI findings.
The Gleason score is used to grade the aggressiveness of prostate cancer based on how the cancer cells look under a microscope. It helps in determining how likely the cancer is to grow and spread.
Workflow: PI-RADS → Biopsy → Gleason Scoring.
Additional Considerations
While the Gleason score is an important factor in understanding prostate cancer's aggressiveness, it is not the only factor considered in determining treatment. Other elements, such as the stage of the cancer (how far it has spread), PSA (Prostate-Specific Antigen) levels, and patient health, all play crucial roles in creating a comprehensive treatment plan.
The Gleason score is just one piece of the puzzle but provides invaluable information that helps physicians and patients make decisions about how to best manage the disease.
Conclusion
In summary, the Gleason score - now also reported as a Grade Group from 1 to 5 - is a key factor in understanding the aggressiveness of prostate cancer. By providing a detailed look at how the cancer cells appear under a microscope, it helps guide treatment decisions and can help predict the cancer's behavior. Gleason 6 (Grade Group 1) usually indicates slow-growing cancer that can often be monitored rather than treated, Gleason 7 covers a range from favorable 3+4 cancers to more serious 4+3 cancers, and scores of 8 to 10 (Grade Groups 4 and 5) point to aggressive disease that calls for prompt, intensive management. It is important for patients to discuss both their Gleason score and Grade Group with their healthcare team to fully understand the implications and decide on the best course of action for their care.
Frequently Asked Questions
Who developed the Gleason grading system?
The system was created in the 1960s by Dr. Donald Gleason, a pathologist at the Veterans Administration hospital in Minneapolis. It has been updated several times since, most notably by the International Society of Urological Pathology in 2005 and 2014, to reflect modern biopsy methods and outcome data.
Can a Gleason score change after prostate surgery?
Yes. A biopsy samples only small cores of tissue, while the whole prostate is examined after a radical prostatectomy. The final pathology can show a higher or lower grade than the biopsy, and upgrading is the more common of the two.
Is it worth getting a second opinion on a prostate biopsy?
It can be, especially when the grade sits near a treatment decision point, such as Grade Group 1 versus Grade Group 2. Grading involves some judgment, and a review by a specialist genitourinary pathologist at a major cancer center sometimes changes the result.
What does cribriform pattern mean on a pathology report?
Cribriform describes a form of pattern 4 cancer in which cells form sheets punctured by small holes, like a sieve. It is linked with a higher risk of the cancer returning or spreading, and its presence may make a man a less suitable candidate for active surveillance.
What is a tertiary Gleason pattern?
A tertiary pattern is a small amount of a third, higher-grade pattern found in addition to the primary and secondary patterns, usually noted after prostatectomy. Pathologists report it because even a small high-grade component can signal a greater risk of recurrence.
Why does the percentage of pattern 4 matter?
Pathologists often report how much of the tumor is pattern 4, particularly in Grade Group 2 cancers. A small percentage may allow some men to consider active surveillance, while a larger share points toward more active treatment.
Can genomic tests add information beyond the Gleason score?
Yes. Tissue-based genomic tests such as Decipher, Oncotype DX Genomic Prostate Score, and Prolaris measure the activity of cancer-related genes in the tumor. Their results can help refine risk estimates, particularly for men deciding between monitoring and treatment.
Can a Gleason score be assigned after radiation or hormone therapy?
Usually not reliably. Radiation and hormone therapy change the appearance of prostate cancer cells under the microscope, so pathologists often note treatment effect instead of assigning a standard Gleason score to tissue taken after these treatments.
More on this topic: Prostate Cancer Publications - Cancer Publications - Men's Health Publications - Prostate Enlargement: Symptoms, Exams, Treatment
Insights, Analysis, and Developments
Editorial Note: Few numbers carry as much weight for a man facing prostate cancer as his grade, and the shift from Gleason scores to Grade Groups is a small change in wording that makes a real difference in understanding. Telling a man he has Grade Group 1 rather than Gleason 6 places him correctly at the bottom of the scale, and separating 3+4 from 4+3 gives him and his doctors a more honest picture of risk. Because a biopsy grade can shift once the whole gland is examined, and because stage, PSA trends, and personal health still count, the grade works best as the start of a conversation rather than the final word - especially for older men weighing treatment side effects against the benefits of careful monitoring.
Author Credentials: Ian C. Langtree is a writer, editor, and the founder and Editor-in-Chief of Disabled World, which he established in 2004 as one of the longest-running independent resources for disability news and information. Over more than two decades, he has written and edited thousands of articles on disability rights, health, accessibility, and assistive technology. Drawing on a global perspective shaped by extensive travel and lived experience, Ian is a committed advocate of the Social Model of Disability, the framework developed by disabled activists in the 1970s that focuses on removing societal barriers rather than on individual impairments. His writing is grounded in that framework and in a lasting commitment to disability rights, accessibility, and social inclusion. To learn more about Ian's background, expertise, and accomplishments, visit his full biography.