Someone who has a Gleason grade of 9 has a lower survival rate than someone who has a smaller Gleason grade. The higher the Gleason score, the more irregular the cancer tissue and the higher the likelihood of the cancer spreading, according to the National Cancer Institute.
The Gleason score is an important indicator in determining the chances of a tumor spreading. It is based on the histologic pattern of prostate cancer tissue as seen under a microscope. In his article for Modern Pathology journal, Peter Humphrey describes the five basic growth patterns that form the primary and secondary patterns. These are added together to form a range between 2 and 10.