Gleason Score & Grade Groups: Understanding Your Pathology Report

What is Gleason score?

The Gleason score is a grading system used to describe how aggressive prostate cancer appears under a microscope. It is the most important factor in determining prognosis and guiding treatment decisions.

The system was developed by Dr. Donald Gleason in the 1960s and remains the gold standard for prostate cancer grading. A higher Gleason score means more aggressive cancer.

How Gleason scoring works – primary + secondary grades

Prostate cancer is graded on a scale of 1 to 5 based on how much the cancer cells resemble normal prostate tissue:

• Gleason 1: Nearly normal (rarely used)
• Gleason 2-3: Well-differentiated (cells look mostly normal)
• Gleason 4: Moderately differentiated (cells look abnormal)
• Gleason 5: Poorly differentiated (cells very abnormal, no gland formation)

The pathologist assigns two grades:

• Primary grade: Most common pattern (at least 50% of the sample)
• Secondary grade: Second most common pattern (5-49% of the sample)
• Gleason score = Primary + Secondary (e.g., 3+4 = 7)

Example:

• If most of the cancer is pattern 3 and a smaller area is pattern 4 → Gleason 3+4 = 7

Gleason score range – 6 to 10

In modern practice, Gleason scores range from 6 to 10 (scores 2-5 are no longer used):

• Gleason 6 (3+3): Low risk – least aggressive
• Gleason 7 (3+4): Favorable intermediate risk
• Gleason 7 (4+3): Unfavorable intermediate risk
• Gleason 8 (4+4): High risk
• Gleason 9-10 (4+5, 5+4, 5+5): Very high risk – most aggressive

Grade Groups (ISUP) – 1 to 5

In 2014, the International Society of Urological Pathology (ISUP) introduced Grade Groups to simplify Gleason score interpretation:

• Grade Group 1: Gleason 3+3 = 6 (Low risk)
• Grade Group 2: Gleason 3+4 = 7 (Favorable intermediate risk)
• Grade Group 3: Gleason 4+3 = 7 (Unfavorable intermediate risk)
• Grade Group 4: Gleason 4+4 = 8 (High risk)
• Grade Group 5: Gleason 9-10 (4+5, 5+4, 5+5) – Very high risk

Gleason 6 (Grade Group 1) – low risk

Gleason 6 (3+3) is the least aggressive form of prostate cancer:

• Risk: Very low risk of metastasis (<1% at 15 years)
• Treatment: Active surveillance is the standard of care (not surgery or radiation)
• Key fact: Gleason 6 cancer does NOT metastasise. It can grow locally but rarely spreads.

Important clarification:

• Gleason 6 is cancer (it can grow and invade locally)
• However, it has extremely low metastatic potential
• Active surveillance (monitoring) is safe and avoids overtreatment

Gleason 7 (Grade Group 2-3) – intermediate risk

Gleason 7 is divided into two subtypes with different prognoses:

Gleason 3+4 = 7 (Grade Group 2 – favorable intermediate):

• Mostly pattern 3 with some pattern 4
• Low to moderate risk of metastasis
• Options: Active surveillance (select patients), surgery, or radiation

Gleason 4+3 = 7 (Grade Group 3 – unfavorable intermediate):

• Mostly pattern 4 with some pattern 3
• Higher risk of progression than 3+4
• Treatment recommended (surgery or radiation + hormone therapy)

Gleason 8-10 (Grade Group 4-5) – high risk

Gleason 8-10 cancers are aggressive and require prompt treatment:

• Gleason 8 (4+4) – Grade Group 4 (High risk): High risk of progression, metastasis
• Gleason 9-10 (4+5, 5+4, 5+5) – Grade Group 5 (Very high risk): Very aggressive, high risk of metastasis and cancer death

Treatment:

• Surgery (radical prostatectomy) with possible lymph node dissection
• Radiation therapy + androgen deprivation therapy (ADT) for 2-3 years
• Multimodal therapy often needed

Prognosis by Gleason score

Gleason Score	Grade Group	Risk Level	10-Year Metastasis Risk
3+3 = 6	1	Low	<1%
3+4 = 7	2	Favorable Intermediate	2-5%
4+3 = 7	3	Unfavorable Intermediate	10-15%
4+4 = 8	4	High	20-30%
9-10	5	Very High	30-50%+

Gleason score and treatment decisions

Gleason score is the most important factor in treatment decisions:

• Gleason 6 (Grade Group 1): Active surveillance (monitoring with PSA, MRI, repeat biopsy)
• Gleason 3+4=7 (Grade Group 2): Active surveillance (select patients) or treatment (surgery/radiation)
• Gleason 4+3=7 (Grade Group 3): Treatment recommended (surgery or radiation)
• Gleason 8 (Grade Group 4): Aggressive treatment (surgery or radiation + hormone therapy)
• Gleason 9-10 (Grade Group 5): Multimodal therapy (surgery + radiation or radiation + long-term hormone therapy)

What is tertiary Gleason pattern?

A tertiary Gleason pattern is a third, higher-grade pattern that comprises less than 5% of the sample. It is reported when present.

• Example: Gleason 3+4 with tertiary pattern 5
• Significance: Even a small amount (5%) of pattern 5 worsens prognosis
• Should be treated as the higher Grade Group (e.g., 3+4 with tertiary 5 behaves more like Grade Group 3 or 4)

Interactive FAQ – Gleason score

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Disclaimer: This information is for educational purposes. Your Gleason score should be interpreted by a urologist in the context of your full clinical picture. Consult a specialist at Vivekananda Hospital.