PI-RADS and Gleason score – how to read the result

Medical author: Arthur Abbazov, MD, urologist, andrologist · Editorial preparation: Wyspa Medycyny Przyjaznej Editorial Team · Medical review: Arthur Abbazov, MD · Date created: 06.08.2026

This article is educational and does not replace a urology consultation or discussion of the results with the treating physician. It is not intended for independent interpretation of an MRI report or biopsy result. Urinary retention, blood in the urine, fever after biopsy, severe lower abdominal or lumbar pain, bone pain, sudden weakness of the lower limbs or rapidly worsening symptoms require urgent medical assessment.

Key information at a glance

• PI-RADS is a suspicion score used in multiparametric MRI of the prostate. It evaluates imaging, not tissue, and does not establish a diagnosis.
• Gleason is a score of the aggressiveness of cancer cells, assessed under a microscope after biopsy. There is no Gleason score without a biopsy.
• Both scales end at 5, but they measure completely different things. There is no conversion such as “PI-RADS 4 means Gleason 8”.
• In practice, the Gleason sum begins at 6 because patterns 1 and 2 are no longer diagnosed in biopsy material. Gleason 6 is the lower limit of the scale, not “6 out of 10”.
• This is precisely why ISUP Grade Groups from 1 to 5 were introduced — so that the lowest risk could be described as 1 rather than 6.
• The order of the numbers in 3+4 and 4+3 matters. The first number represents the dominant pattern.
• PI-RADS 1 and 2 generally argue against clinically significant cancer, PI-RADS 4 and 5 support suspicion of it, while PI-RADS 3 is an equivocal category requiring an individual decision.
• MRI and biopsy results are always interpreted together with PSA, digital rectal examination, age, comorbidities and the patient’s medical history.
• Not every diagnosis of prostate cancer means immediate treatment. For the lowest-risk disease, guidelines allow active surveillance, meaning planned observation with regular follow-up.
• The decision about further management is made by the physician together with the patient, not by a single number in the report.

Learn more about the specialist

Arthur Abbazov, MD, is a urologist and andrologist at Wyspa Medycyny Przyjaznej in Gdańsk. He diagnoses and treats diseases of the male genitourinary system, including prostate-related symptoms, urinary disorders and discussion of imaging and laboratory results with patients. Consultations are also available in Russian.

Learn more about Arthur Abbazov, MD

Two scales, two different questions

The most common misunderstanding is treating PI-RADS and Gleason as two versions of the same assessment. They are not. These are two different tests, performed at two different stages of diagnosis, answering two different questions.

The practical conclusion is simple. If a patient only has an MRI result, there is no diagnosis yet. If a biopsy result is available, PI-RADS is no longer the most important number in the medical documentation.

What is PI-RADS?

PI-RADS stands for Prostate Imaging Reporting and Data System. It is a standardised method for reporting multiparametric MRI of the prostate, developed so that reports from different centres are comparable and understood in the same way by radiologists and urologists. The current version is PI-RADS v2.1.

The radiologist evaluates visible lesions across several imaging sequences, including T2-weighted images, diffusion-weighted imaging with ADC maps, and post-contrast sequences. The sequence that carries the greatest weight depends on the zone of the prostate in which the lesion is located. On this basis, the lesion is assigned a category from 1 to 5.

It is worth noting the term “clinically significant”. PI-RADS is not designed to detect every microscopic change. The system is intended to identify cancers that may genuinely threaten the patient, rather than lesions that would never cause symptoms during the patient’s lifetime.

Why does PI-RADS 3 raise the most questions?

PI-RADS 3 is an intermediate category. The image does not look entirely reassuring, but neither is it clearly suspicious. A patient reads “equivocal” and perceives this as a lack of an answer, while the physician interprets it as a sign that the decision must be based on more than MRI alone.

With PI-RADS 3, the urologist considers factors including PSA level, PSA density in relation to prostate volume, PSA kinetics over time, digital rectal examination findings, age, family history, previous biopsies, and the patient’s concerns and expectations. In one case, biopsy may be reasonable; in another, follow-up after several months. This is not indecision on the part of the physician, but a consequence of the fact that category 3 is, by definition, inconclusive.

What is the Gleason score?

The Gleason score describes how much the architecture of the tumour differs from normal prostate gland tissue. The pathologist examines the arrangement of glands in the sampled tissue under a microscope and assigns a pattern from 1 to 5, where pattern 1 most closely resembles normal tissue and pattern 5 differs from it the most.

Several patterns often coexist within a prostate cancer sample. Therefore, the result is reported as the sum of two numbers. In biopsy material, the first number represents the dominant pattern, meaning the one occupying the largest proportion of the tumour tissue, while the second number represents the highest-grade pattern among the remaining tissue. This is why results such as 3+3, 3+4, 4+3 or 4+5 are used.

A key point: Gleason describes the appearance of the cancer tissue, not tumour size, disease stage or prognosis on its own. It is one of several elements of risk assessment, not the entire assessment.

Why does the Gleason scale start at 6 rather than 2?

This is the part that usually requires the most explanation during a consultation. A patient sees “Gleason 6” and calculates: six out of ten, more than half, therefore bad. This misunderstanding can have serious emotional consequences because it causes panic in a situation that is actually at the most favourable end of the scale.

The explanation is historical. The scale was developed in the 1960s and originally included patterns from 1 to 5, theoretically allowing sums from 2 to 10. Over time, it was established that patterns 1 and 2 should no longer be diagnosed in core biopsy material because in such small samples they cannot be reliably distinguished from non-cancerous changes. In practice, the lowest pattern recognised today is pattern 3.

If the lowest pattern is 3, the lowest possible sum is 3+3, which equals 6. Gleason 6 is not the middle of the scale. It is the lower limit of the scale. A patient with a 3+3 result has the least aggressive form that can be diagnosed on biopsy.

This is why a parallel terminology was introduced: ISUP Grade Groups from 1 to 5. Gleason 6 corresponds to ISUP Grade Group 1. This change had no biological significance. It had a communication purpose, because “Group 1 out of 5” reflects the true situation much better, while “6” sounds considerably worse than it actually is.

ISUP Grade Groups — how to read a biopsy result

Many pathology reports now provide both pieces of information at the same time: the Gleason sum and the corresponding Grade Group. The table below shows how they relate.

The ISUP Grade Group is not the only criterion. European guidelines combine tumour grade with PSA level and local disease stage to assign the patient to a risk category. Only this overall assessment, rather than a single number, forms the basis for a discussion about treatment.

Gleason 3+4 or 4+3 — why does the order matter?

Both results add up to 7, but they do not mean the same thing. The first number is the dominant pattern, meaning the one that occupies the greater proportion of the tumour tissue.

With 3+4, the less aggressive pattern predominates and pattern 4 forms the smaller component. With 4+3, the proportions are reversed and the more aggressive pattern predominates. Therefore, 3+4 corresponds to ISUP Grade Group 2, whereas 4+3 corresponds to Grade Group 3, despite the identical total.

This is a good example of why simply adding the numbers can be misleading. A patient who only remembers “seven” does not have the full information about the result.

Can PI-RADS be converted into Gleason?

No. There is no conversion formula, table or equation that turns a PI-RADS category into a Gleason sum. This question comes up very often, and the answer is unambiguous.

The only general statement that can be made is that the higher the PI-RADS category, the greater the probability that biopsy will reveal clinically significant cancer. But this is a statistical relationship observed across groups of patients, not a prediction for a specific individual. A PI-RADS 5 lesion may sometimes yield a negative biopsy, and a PI-RADS 3 lesion may sometimes reveal a cancer that requires treatment.

MRI indicates where tissue should be sampled. Only the pathologist can determine what that tissue actually is.

What do PI-RADS and Gleason not tell you?

Understanding what cannot be inferred from the result is just as important as understanding what can. Neither the PI-RADS category nor the Gleason sum alone tells you:

• the patient’s prognosis,
• whether the disease has spread beyond the prostate,
• whether there are lymph-node or bone metastases,
• which treatment will be best in a particular case,
• whether treatment is needed immediately,
• how the disease will behave over the coming years,
• how the result will affect sexual function and urinary continence, because this depends on the selected treatment method,
• whether the biopsy result reflects the entire prostate, because biopsy evaluates only the sampled tissue fragments.

Answering these questions requires combining the result with PSA, clinical examination, additional imaging in selected cases, and the patient’s general health and expectations.

A diagnosis does not always mean immediate treatment

For many patients, the most surprising information is that guidelines allow active surveillance in the lowest-risk disease. This is not abandoning treatment or sending the patient away without a plan. Active surveillance is a structured programme of observation: regular PSA measurements, follow-up appointments, clinical examinations, and repeat imaging or biopsies according to an established schedule.

The reason for this approach is that some prostate cancers develop very slowly and may not threaten the patient for many years. Immediate radical treatment, on the other hand, carries a real risk of complications, including erectile dysfunction and urinary incontinence. Active surveillance allows these risks to be deferred while preserving the option of treatment if the disease begins to progress.

Qualification for active surveillance is not automatic and does not depend on the ISUP Grade Group alone. It depends on PSA, the number and extent of positive biopsy cores, MRI findings, age, comorbidities and the patient’s decision, including willingness to undergo regular follow-up.

When do symptoms require urgent assessment?

A PI-RADS or Gleason result alone is not an emergency. The following symptoms, however, require urgent assessment:

• urinary retention, meaning an inability to pass urine despite the urge,
• blood in the urine or semen, especially if heavy,
• fever, chills or deterioration in general condition after prostate biopsy,
• severe pain in the lower abdomen, perineum or lumbar region,
• bone pain, especially in the spine or pelvis, that persists and worsens,
• weakness or numbness of the lower limbs, difficulty walking,
• sudden loss of bladder or bowel control,
• unintentional weight loss accompanied by increasing weakness.

In such situations, you should not wait for the next scheduled appointment or for the result of another test.

Common myths about PI-RADS and the Gleason score

• “Gleason 6 means six out of ten.” No. It is the lowest score currently diagnosed on biopsy and corresponds to ISUP Grade Group 1.
• “PI-RADS 4 means cancer.” No. It means that cancer is likely based on imaging. The diagnosis is established by biopsy.
• “PI-RADS 2 rules out cancer.” No. It lowers the probability of clinically significant disease but does not remove the need for further PSA monitoring and follow-up.
• “3+4 and 4+3 are the same because both equal 7.” No. The order indicates the dominant pattern and corresponds to different ISUP Grade Groups.
• “A high PI-RADS means a high Gleason score.” No. There is no conversion between these scales.
• “A diagnosis of prostate cancer always means immediate surgery.” No. For the lowest-risk disease, guidelines allow active surveillance.
• “If the biopsy did not show cancer, then it definitely is not there.” Not always. Biopsy evaluates only sampled tissue, so persistent suspicion may require further follow-up.
• “You can simply compare the result with an online table.” No. The same result in two patients may lead to completely different clinical decisions.

Do you have a prostate MRI or biopsy result and are unsure what it actually means?

A single number is not enough to make a decision. A urology consultation allows the result to be interpreted together with PSA, clinical examination and your health situation, and the next steps to be discussed.

Discussion of prostate test results at Wyspa Medycyny Przyjaznej in Gdańsk

At Wyspa Medycyny Przyjaznej, Arthur Abbazov, MD, consults patients with urological symptoms and with test results that require discussion: elevated PSA, a prostate MRI report, a biopsy result or an abnormal digital rectal examination. The purpose of such a consultation is to translate medical documentation into understandable language and determine what should happen next.

During the consultation, the physician compares the result with the patient’s history, previous PSA measurements, symptoms and comorbidities. Depending on the situation, this may lead to observation and follow-up, further diagnostic testing or referral to a centre providing oncological treatment. The current scope of services, physician availability, prices and preparation instructions should be confirmed at registration.

Learn more about Arthur Abbazov, MD Urology consultation Urology

What should you ask the urologist when discussing your result?

• Does my MRI result mean that I need a biopsy?
• What PI-RADS category was assigned and in which zone of the prostate?
• If I have PI-RADS 3, what are the arguments for biopsy and what are the arguments for observation?
• What is my Gleason sum and which ISUP Grade Group does it correspond to?
• Does pattern 3 or pattern 4 predominate in my result?
• In how many biopsy cores and in what proportion was the lesion identified?
• Which risk category do I fall into when the result is considered together with PSA and clinical examination?
• Is active surveillance possible in my case?
• What other tests are needed before making a decision?
• What treatment methods are available and what risks of complications do they carry?
• How might the selected management affect urinary continence and sexual function?
• When should I return for follow-up and which symptoms require an earlier appointment?

FAQ — PI-RADS and the Gleason score

What is PI-RADS?

PI-RADS is a standardised reporting system for multiparametric MRI of the prostate. It uses categories from 1 to 5 to describe how strongly a visible lesion resembles clinically significant cancer. It is not a diagnosis.

Does PI-RADS 4 mean prostate cancer?

No. It means that clinically significant cancer is likely and usually represents an indication for targeted biopsy. The diagnosis is established only by microscopic examination of the sampled tissue.

What does PI-RADS 3 mean?

It is an intermediate category, meaning the imaging is equivocal. The decision about biopsy, follow-up MRI or observation depends on PSA, PSA density, clinical examination, age and risk factors. By definition, this category is not conclusive.

What is the Gleason score?

It is a microscopic grading system used to assess the aggressiveness of prostate cancer. The pathologist assesses how much the tumour architecture differs from that of a normal prostate gland and reports the result as the sum of two patterns, for example 3+4.

Why does the Gleason scale start at 6?

Because patterns 1 and 2 are no longer diagnosed in core biopsy material. The lowest recognised pattern is 3, so the lowest possible sum is 3+3, which equals 6. Gleason 6 is the lower limit of the scale, not its middle.

What are ISUP Grade Groups?

They are a simplified grading system from 1 to 5, introduced in part so that the lowest risk is described as Group 1 rather than the number 6. Gleason 6 corresponds to Group 1, Gleason 3+4 to Group 2, Gleason 4+3 to Group 3, Gleason 8 to Group 4, and Gleason 9 and 10 to Group 5.

What is the difference between Gleason 3+4 and 4+3?

The first number represents the dominant pattern. In 3+4, the less aggressive pattern predominates; in 4+3, the more aggressive pattern predominates. The total is the same, but the results correspond to different ISUP Grade Groups and may lead to different clinical decisions.

Can PI-RADS be converted into Gleason?

No. There is no conversion between these scales. A higher PI-RADS category is associated with a greater probability of detecting clinically significant cancer on biopsy, but it does not predict a specific Gleason score in an individual patient.

Does Gleason 6 require immediate treatment?

Not always. In selected patients with the lowest-risk disease, guidelines allow active surveillance, meaning planned observation with regular follow-up. Qualification is individual and depends on several parameters, not on the ISUP Grade Group alone.

Does a negative biopsy rule out prostate cancer?

Not in every situation. A biopsy evaluates only the sampled tissue fragments. If suspicion persists, PSA continues to rise or MRI remains suspicious, the physician may recommend further follow-up or repeat diagnostic testing.

Does a PI-RADS or Gleason result determine prognosis?

Not by itself. It is one component of risk assessment. A complete picture requires correlation with PSA, local disease stage, age, comorbidities and, in some cases, additional imaging.

Who discusses prostate test results at WMP?

On the WMP website, Arthur Abbazov, MD, is described as a urologist and andrologist who diagnoses and treats diseases of the male genitourinary system. A urology consultation includes discussion of test results and determination of further management.

Sources

• European Association of Urology, EAU-EANM-ESTRO-ESUR-ISUP-SIOG Guidelines on Prostate Cancer: https://uroweb.org/guidelines/prostate-cancer
• American College of Radiology, PI-RADS Prostate Imaging Reporting and Data System: https://www.acr.org/Clinical-Resources/Clinical-Tools-and-Reference/Reporting-and-Data-Systems/PI-RADS
• Turkbey B. et al., Prostate Imaging Reporting and Data System Version 2.1, European Urology 2019: https://pubmed.ncbi.nlm.nih.gov/30898406/
• Epstein J.I. et al., The 2014 International Society of Urological Pathology (ISUP) Consensus Conference on Gleason Grading of Prostatic Carcinoma: https://pubmed.ncbi.nlm.nih.gov/26492179/
• NICE, Prostate cancer: diagnosis and management (NG131): https://www.nice.org.uk/guidance/ng131
• NHS, Prostate cancer: https://www.nhs.uk/conditions/prostate-cancer/
• NHS, PSA test: https://www.nhs.uk/tests-and-treatments/psa-test/
• Cancer Research UK, Grades of prostate cancer and Gleason score: https://www.cancerresearchuk.org/about-cancer/prostate-cancer/stages/grades-gleason-scores
• National Cancer Institute, Gleason score — definition: https://www.cancer.gov/publications/dictionaries/cancer-terms/def/gleason-score
• National Cancer Institute, Prostate Cancer Treatment (PDQ) — Patient Version: https://www.cancer.gov/types/prostate/patient/prostate-treatment-pdq
• Pacjent.gov.pl, prostate cancer: https://pacjent.gov.pl/artykul/rak-prostaty
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