Can someone explain how the Gleason score works

From Wikipedia:
http://en.wikipedia.org/wiki/Gleason_score

Basically, the gleason grades the aggresiveness of the cancer cells when examined under the microscope. The doctor who created this system - Donald Gleason - created this system to provide a measuring system of the cancer and what might be the possible treatments based on the aggresssiveness of the disease. A grade 1 cancer are cells that look relatively normal to a healthy prostate cell. A grade 2 begins to look more abnormal and multiplies in a more mutated way. A grade 3 is moderate, 4 and 5 do not look like normal prostate cells. In fact they are the highly aggresive forms of the disease. Gleason took this grading system a bit further by creating the Gleason sum. After examining the tissue, there may be multiple grades of the disease in a core sample. The Gleason Sum is the grade sum of the two most predominant cancer cell types. The lowest possible score is 2. The highest is 10. Thats why you see 3+3 for a moderate cancer cell invasion. 4+3 in my case, a Gleason 7, is more dangerous than a 3+4. The first number is the most predominant cancer grade. My 4+3 will behave more like a Gleason 8, while a 3+4 will behave more like a Gleason 6. Thats a bit confusing but when you see the scores above 3+4, you see the reason for more concern as this person is at high risk for metastatic disease. This alone does not mean the outcome of a patient however. PSA, positive margins, pathalogical stage all combined with the Gleason will provide a better look into the future. It is possible a Gleason 10 will never have recurrance but is is nearly 100% likely that because of the ability of these cells to rapidly multiply will mean recurrance is likely. All scores are cancer. And recurrance is always possible after surgery, radiation, HT or what ever the treatment. A low Gleason, say a 5, is still dangerous if the stage is T3 or above. But is is less likely to be a fast process. A Gleason 10 is likely to recur and the patient will have a poor prognosis.