When a biopsy confirms the presence of cancer, the next step is to determine the level of aggressiveness (grade) of the cancer cells. In a laboratory, a pathologist examines a sample of your cancer to determine how much cancer cells differ from the healthy cells. A higher grade indicates a more aggressive cancer that is more likely to spread quickly.

The most common scale used to evaluate the grade of prostate cancer cells is called a Gleason score. Scoring is based upon the combination of two numbers, with a range from 2 (nonaggressive cancer) to 10 (very aggressive cancer).