A Gleason score of 6 means the prostate cancer is considered low-grade and typically grows and spreads slowly, explains The American Cancer Society. A Gleason score between 8 and 10 means that cancer is high-grade and very aggressive. Gleason scores of 7 are middle-grade.
The Gleason score is comprised of two combined grades, according to the American Cancer Society. The two grades are added together after evaluating the tumor and cancerous cells. Tissue that looks normal is given a grade of 1, while abnormal tissue is rated at a 5. The highest score a person can receive using the Gleason system is a 10.
A person can have different Gleason scores depending on the area of the tumor or cancerous tissue that is measured, states The American Cancer Society. However, the highest score is considered to be the official Gleason score, and that is the one used in diagnosing the cancer and for potential treatments.
In order to test the tissues and obtain an accurate Gleason score, a physician completes a core-needle biopsy in different areas of the prostate, reports The American Cancer Society. The most common type of prostate cancer is adenocarcinoma. In addition to the biopsy, there are several other factors that are important to a proper diagnosis and treatment options, including PSA levels, the number of cores that contain the cancer, and whether or not cancerous cells have been found in both sides of the prostate.