The Gleason Grading System

The Gleason Grading System is used to evaluate or "grade" prostate cancer cells obtained by needle biopsy. A pathologist will look at the biopsied prostate tissue under a microscope. The pathologist will examine the way that the cancerous cells look compared to normal prostate cells. If the cancerous cells appear to resemble the normal prostate tissue very closely, they are said to be very well differentiated and are considered to be Gleason grade 1. This means that the tumor is not expected to be fast growing. On the other hand, if the cells in question look fairly irregular and very different from the normal prostate cells, then they are very poorly differentiated and are assigned a Gleason grade 5. Grades 2-4 are used for tumors that fall between grades 1 and 5 with higher numbers corresponding to a faster growing tumor. Because prostate cancer tissue is often made up of areas that have different grades, the pathologist will closely examine the areas that make up the largest portion of the tissue. Gleason grades are then given to the two most commonly occurring patterns of cells. Once the two grades have been assigned, a Gleason score can be determined. This is done by adding together the sum of the two Gleason grades.  Gleason scores range from 2 to 10. The higher the score, the more aggressive the cancer. The most commonly diagnosed score is 3+3=6. You should thoroughly discuss your results with your physician. Your doctor can explain what your Gleason score, along with your other risk criteria for your individual situation.