The Gleason score is a number pathologists use to describe prostate cancer based on how the tumor cells look under a microscope. This score helps doctors predict how quickly and aggressively the cancer may grow and spread. The Gleason score can only be determined after examining a tissue sample from the prostate tumor.
To calculate the Gleason score, pathologists first give the cancer cells a grade from 3 to 5, based on how closely the cancer resembles normal prostate tissue:
Grade 3: Cancer cells look similar to normal prostate glands and typically grow slowly.
Grade 4: Cancer cells look less like normal prostate glands, grow faster, and have a higher chance of spreading.
Grade 5: Cancer cells look very different from normal glands, grow quickly, and are likely to spread aggressively.
Grades 1 and 2 were used historically but are no longer diagnosed today.
Once the grades are assigned, the two most common grades in the tumor are combined to determine the Gleason score. For example:
If the tumor is mostly grade 3 (70%) and partially grade 4 (30%), the Gleason score is 3+4=7.
If the tumor is entirely grade 3, the Gleason score is 3+3=6.
Gleason score 6 (3+3): These tumors are low-grade, grow slowly, and rarely spread. They usually require close monitoring through active surveillance rather than immediate treatment.
Gleason score 7 (3+4 or 4+3): These tumors are intermediate-grade. They have a moderate risk of growing or spreading, falling between low-grade and high-grade tumors in terms of aggressiveness.
Gleason scores 8 to 10 (4+4, 4+5, 5+4, or 5+5): These tumors are high-grade and very different from normal prostate tissue. They tend to grow quickly and have a higher chance of spreading. Aggressive treatment is usually recommended for these tumors.
Understanding your Gleason score helps you and your healthcare team choose the best treatment plan based on your specific type of prostate cancer.