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 describes the level 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 a lot different than normal prostate cells. If the cancer is well-differentiated, then it looks more 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 the sum of two Gleason grades added together. The grade is a number from 1 to 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. 
• A secondary grade is given to the cells that make up the rest of the tumor. 
• The Gleason score is 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 Gleason score. For example:

• In a report of Gleason 7 (3+4), most of the tumor is made up of cancer cells that are grade 3.
• In a report of Gleason grade 4, score 7, most of the tumor is made up of cancer cells that are grade 4, with the total score being 7 (grade 3 cancer cells make up the rest of the tumor). 

When a prostate is biopsied for diagnosis and then later removed with a radical prostatectomy, Gleason scores are the same from the biopsy and surgery samples about 7 to 8 times out of 10. 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. Having a lower Gleason score at surgery than from the biopsy happens in less than 1 out of 20 men. These differences can be due to an incomplete biopsy or the skill of the pathologist. It is important to have your tumor looked at 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 treat prostate cancer.