The Gleason System Prostate Cancer Grading System
The Gleason System
In addition to the stage of disease, your doctor will assign a grade to the tumor. A grade is an indication of how aggressive the cancer is by the way it looks under the microscope.
Prostate cancer has its own unique grading system called the Gleason System. To assign a Gleason Grade, a tissue sample will be taken of your tumor and a pathologist will view it under a microscope. He or she will then assign a Gleason Grade to the tumor based on what the cells look like and how they are arranged under the microscope. The cells are assigned a number between 1 and 5. Grade 1 is the least aggressive form of cancer. These cells almost look like healthy prostate cells. Grade 5 is the most aggressive. These cells don’t look anything at all like healthy cells.
The prostate cancer may also contain more than one cell pattern thus more than one grade. When this occurs, the tumor is assigned another number that indicates the two most commonly occurring cells in the tumor. The grades are then added together for the final Gleason score, which can range from 2 to 10.
Your doctor may also refer to the "ploidy status" of the prostate cancer cells. Diploid cancer cells, for example, are the slowest growing and the least likely to spread. Aneuploid cells are more aggressive and may spread throughout the body. Tetraploid cells fall somewhere in between the two. The "ploidy status" of cells is related to the Gleason Grade of the tumor.
These are tables constructed on the basis of the PSA, stage, grade and surgical findings of over 4,000 men. The tables are used to predict the probability that the prostate cancer has spread to the lymph nodes, seminal vesicles, penetrated the capsule or remains confined to the prostate.