These well differentiated cancers grow and spread out more slowly than poor differentiated or totally undifferentiated cancer.
Here is the original GLEASON diagram that illustrates the 5 grades of prostatic cancer, from grade 1 well differentiated, to undifferentiated grade 5.
Prostate cancer is usually a polymorphic tumor in which we meet several clones of diverse cells tumoral differentiation.
It is necessary to consider the respective grade of both clones of cancerous tissues the most represented in the studied sample of the tumor and add these two grades.
We so obtain a number, from 2 to 10, which represents the GLEASON score of this cancer.
The tumors of score 2 to 4 are cancers of low malignancy, from 5 to 7 intermediate risk of malignancy and the scores from 8 to 10 correspond to the prostate cancer of high risk, the most aggressive and evolutionary.