Gleason Score

What Is a Gleason Score?

The Gleason score is a standardized grading system used to determine how aggressive prostate cancer is likely to be. It is based on the microscopic examination of prostate tissue obtained during a biopsy. By evaluating how abnormal the cancer cells appear, the Gleason score helps predict how quickly the cancer may grow or spread and plays a key role in guiding treatment decisions.

How the Gleason Score Is Determined

Developed in the 1960s by Dr. Donald Gleason, this scoring system remains a cornerstone of prostate cancer diagnosis and management. Pathologists evaluate the two most common patterns of cancer cells present in the tissue sample.

Each pattern is assigned a grade from 1 to 5:

• Grade 1 closely resembles normal prostate tissue

• Grade 5 appears highly abnormal and aggressive

The grades of the primary (most common) and secondary (second most common) patterns are added together to calculate the Gleason score. Although the theoretical range is 2 to 10, scores below 6 are rarely used in practice, as grades 1 and 2 closely resemble benign tissue. As a result, most reported Gleason scores fall between 6 and 10.

What the Gleason Score Means

• Gleason score 6 (3+3): Indicates low-grade cancer with well-differentiated cells that tend to grow slowly and are less likely to spread.

• Gleason score 7: May be reported as 3+4 or 4+3. A score of 4+3 suggests a higher proportion of more aggressive cells and a greater risk than 3+4.

• Gleason scores 8–10: Represent high-grade cancer with poorly differentiated cells that are more likely to grow rapidly and spread beyond the prostate.

Understanding your Gleason score is essential in determining the most appropriate treatment approach. For lower-risk cancers, active surveillance may be recommended, while higher-risk cases may require more aggressive treatment such as surgery, radiation therapy, or hormone-based therapies.