Gleason grade

The Gleason grade is a system pathologists use to describe how prostate cancer cells look under a microscope. It helps doctors understand how aggressive a type of prostate cancer called adenocarcinoma might be. The Gleason grade can only be determined after examining a sample of the tumor.

How do pathologists determine the Gleason grade?

To determine the Gleason grade, pathologists examine prostate cancer cells under a microscope and compare them to normal prostate glands. Each area of cancer is given a number between 1 and 5. Tumors that closely resemble normal glands get lower numbers (3), indicating slower growth and a lower risk of spreading. Tumors that look very different from normal glands get higher numbers (4 or 5) and are more aggressive, growing quickly, and are more likely to spread.

It’s important to note that grades 1 and 2 are no longer used in modern practice. These grades were historically significant but are essentially never diagnosed today. This means the Gleason grades currently range from 3 to 5.

What is a Gleason score?

The Gleason score is calculated by adding the two most common Gleason grades found in the tumor. If a tumor has only one Gleason grade throughout, that grade is doubled. For example:

• If 70% of the tumor is grade 3 and 30% is grade 4, the Gleason score is 3+4=7.
• If the tumor is entirely grade 3, the Gleason score is 3+3=6.

The Gleason score helps doctors predict the likely behavior and growth pattern of the tumor.

What do different Gleason scores mean?

• Gleason score 6 (3+3): These tumors are low-grade and closely resemble normal prostate glands. They usually grow slowly, rarely spread, and can often be managed through careful monitoring known as active surveillance.
• Gleason score 7 (3+4 or 4+3): These tumors are intermediate-grade and somewhat resemble normal glands. They have a moderate risk of growing or spreading and fall between low-grade and high-grade tumors in terms of aggressiveness.
• Gleason scores 8 to 10 (e.g., 4+4, 4+5, 5+4, or 5+5): These tumors are high-grade, meaning they look very different from normal prostate tissue and have a higher chance of growing rapidly and spreading aggressively.

Understanding the Gleason score helps you and your healthcare team choose the most effective treatment plan based on the aggressiveness of the cancer.