What is a Gleason score?

A Gleason score is a measure of tumor aggressiveness. It's scored from two to 10, with 10 being most aggressive and two being least aggressive. If your Gleason score is six or less, you're often a candidate for active cancer surveillance.

Cells removed from the prostate gland during a biopsy are examined under a microscope by a pathologist. He or she evaluates the most common type of cell in the biopsy and assigns a numerical score based on how different the cells are from normal, healthy prostate cells. The score ranges from a Gleason pattern 1, meaning the cells look similar to normal prostate tissue, to Gleason pattern 5, which means the cells have characteristics of aggressive prostate cancer.

The same grading process is repeated for the second most common type of cell in the biopsy specimen.

The higher the Gleason score, the more likely the cancer will spread beyond the prostate gland.

The scoring system is named after Donald Gleason, a pathologist at the Minneapolis Veterans Affairs Hospital, who developed it with other colleagues in the 1960s.

A prostate biopsy is used to confirm the diagnosis. The tissue is viewed with a microscope and the results are reported using a Gleason grade and a Gleason score. The Gleason grade is based on how the cells vary from normal prostate cells. The cells are graded on a scale of 1 – 5 and reflect the aggressiveness of the tumor. More than one Gleason grade is often present. Therefore, the 2 predominant grades are added to give a Gleason score. In general, the higher the Gleason score, the more likely the cancer is to spread beyond the prostate gland:

• Scores 2 - 4: Low-grade cancer
• Scores 5 - 7: Intermediate- (or in the middle-) grade cancer. Most prostate cancers fall into this category.
• Scores 8 - 10: High-grade cancer (poorly-differentiated cells)

If the Gleason score is low in an older individual, watchful waiting (often called active surveillance) may be a good option. This is because the cancer may not readily spread or cause any symptoms.