STAGE 1: The cancer is located on one side of the prostate. At this stage, the tumor is very small or found incidentally, possibly during surgery or by an elevated prostate-specific antigen (PSA) level. The Gleason score is low.
STAGE 2: The cancer is located only in the prostate but can be seen on imaging scans or felt during a digital rectal exam. The Gleason score may range from 2 to 10.
STAGE 3: The cancer has extended through the outer layer of the prostate and into surrounding tissues and may be found in the seminal vesicle but not in the lymph nodes. The Gleason score may range from 2 to 10.
STAGE 4: The cancer has spread to the lymph nodes near or far from the prostate or has spread to distant tissues or organs, such as the liver or bones. The Gleason score may range from 2 to 10.
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The Gleason grading system defines prostate cancer by grade based on the pathologist’s review of a biopsy or surgical specimen, with 1 being the least aggressive and 5 being the most aggressive. The grade of the most common tumor pattern is added to the grade of the second most common tumor pattern in the tissue examined to create the Gleason score. A Gleason score of 2 to 4 is considered low grade, 5 to 7 is intermediate grade and 8 to 10 is high grade.