Gleason Grade and Score

The Gleason score is named after Dr. Donald Gleason, a pathologist who studied prostate cancer cells. He made a scoring tool to help set apart the less aggressive prostate cancers from the more aggressive ones. The tool shows the "grade" of the tumor, which is a measure of the degree of differentiation of prostate cancer cells. Differentiation means how "normal" a cancer cell looks under a microscope when compared to a normal prostate cell. If the cancer is poorly differentiated or undifferentiated, then it looks very abnormal. If the cancer is well-differentiated, then it looks like normal cells.

More aggressive cancers are poorly differentiated. These tumors grow quickly and multiply in an uncontrolled way. Your Gleason score helps guide treatment options.

The Gleason score is a sum of two Gleason grades added together. The grade is a number from 1-5, with 1 being the most well-differentiated (looks more like normal cells) and 5 being the most poorly differentiated (looks more abnormal). The pathologist gives a primary grade to the tumor cells that make up most of the tumor and a secondary grade to the cells that make up the rest of the tumor. The Gleason score is then the sum of these two grades. So, Gleason scores could be from 2 (which is 1+1) to 10 (which is 5+5). The grade that stands out the most (primary) is either reported as the Gleason grade or is the first number in the score. For example:

• In a report of Gleason 7 (3+4), grade 3 is the most prominent.
• In a report of Gleason grade 4, score 7; grade 4 is the most prominent, with the total score being 7 (therefore grade 3 is the second most prominent score).

When a prostate is biopsied for diagnosis and then later removed with a radical prostatectomy, Gleason scores are the same between the biopsy and surgery samples about 75% of the time. In about 1 out of 5 of the cases, the surgery sample ends up having a higher Gleason score (which means a more aggressive cancer) than what was found on the first biopsy. The reverse (lower Gleason score at surgery than at biopsy) happens for less than 1 out of 20 men. These differences can be due to an incomplete biopsy or the skill of the pathologist. Because it is based on the pathologist’s interpretation, it is important to have your tumor reviewed by an expert pathologist. Many experts suggest having a second pathologist review the sample to be sure the Gleason grading is right.

The Gleason score is a very strong tool in helping to treat prostate cancer.