Physicians characterize the aggressiveness of prostatecancer using the Gleason grading system, which provides an estimate of the cancer's potential to grow and spread to other parts of the body. The pathologist determines the Gleason grade based on how closely the cells of the gland resemble those of a normal prostate. Once the prostate is removed during surgery, a pathologist examining the prostate assigns a grade to the most common tumor, known as the primary Gleason grade, and a second grade to the next most common tumor, known as the secondary Gleason grade. The two grades are added together to get a Gleason score, also known as the Gleason sum.
