Gleason Score

What is a Gleason score?

A Gleason score is a grading system for prostate cancer. If you have prostate cancer, your Gleason score is based on what pathologists know about your situation after viewing tissue samples under a microscope. It’s one of the ways healthcare providers classify prostate cancer as they develop treatment plans or set prognoses (what you can expect after treatment).

How are Gleason scores calculated?

Medical pathologists calculate Gleason scores by studying tissue samples under a microscope. If you have prostate cancer, your prostate tissues have cells that are mutating or changing from normal cells to abnormal or cancerous cells.

Early on, cancerous cells can masquerade as healthy cells. Over time, cancerous cells look less like healthy cells. Pathologists grade each tissue sample on a 1 to 5 scale. The lower the grade, the more cancer cells look like normal cells:

• Grade 1: The cancerous cells look a lot like normal cells.
• Grades 2-4: Cancerous cells in the tissue look less like normal cells.
• Grade 5: Cancerous cells look very abnormal.

Each area of prostate cancer may have a different grade, so pathologists pick the two areas that make up most of the cancer. They add the two areas’ grades to come up with a Gleason score.

For example, if the largest area with cancer is Grade 3 and the next largest area is Grade 5, the Gleason score is 8. Any area with a combined Gleason score of 6 or higher is considered cancerous.

What’s a normal Gleason score?

Your Gleason score doesn't rank potential ranges like ranges set for elevated PSA (prostate-specific antigen) tests. Instead, providers break Gleason scores into three categories:

• Gleason 6: The cells look like healthy cells, which is called well differentiated.
• Gleason 7: The cells look somewhat like healthy cells, which is called moderately differentiated.
• Gleason 8, 9 or 10: The cells look very different from healthy cells, which is called poorly differentiated or undifferentiated.

What is a good Gleason score for prostate cancer?

A Gleason score isn’t good or bad, per se. Knowing your Gleason score is one way that healthcare providers predict how quickly prostate cancer might grow. Gleason scores range from 6 (low-grade cancer) to 10 (high-grade cancer). Low-grade prostate cancer grows more slowly than high-grade cancer and is less likely to spread (metastasize).

It’s important to remember your Gleason score is just one of several pieces of information providers use to plan treatment or set a prognosis. They also consider the results of other tests and more biopsy information.

For example, when you had your biopsy, your healthcare provider obtained several samples or cores from your prostate. They checked how many cores had cancerous cells and whether most of the cells in the cores were cancerous cells. Other factors may include:

• Blood PSA level.
• Digital rectal exam results.
• Imaging test results like ultrasound, magnetic resonance imaging (MRI) or positron emission tomography (PET) scan.
• If there’s cancer in both sides of your prostate.
• If prostate cancer spread to other areas of your body.