Prostate cancer is diagnosed after a biopsy. One or more tissue samples are taken from the prostate and examined under the microscope.
The Gleason grading system refers to how abnormal your prostate cancer cells look and how likely the cancer is to advance and spread. A lower Gleason grade means that the cancer is slower growing and not aggressive.
The first step in determining the Gleason grade is to determine the Gleason score.
- When looking at cells under the microscope, the doctor assigns a number (or grade) to the prostate cancer cells between 1 and 5.
- This grade is based on how abnormal the cells appear. Grade 1 means that the cells look like normal prostate cells. Grade 5 means that the cells look very different from normal prostate cells.
- Most prostate cancers contain cells that are different grades. So the two most common grades are used.
- The Gleason score is determined by adding the two most common grades. For example, the most common grade of the cells in a tissue sample may be grade 3 cells, followed by grade 4 cells. The Gleason score for this sample would be 7.
Higher numbers indicate a faster growing cancer that is more likely to spread.
Currently the lowest score assigned to a tumor is grade 6. Scores below a 6 show normal to near- normal cells. Most cancers have a Gleason score of between 5 and 7.
Gleason Grading System
Sometimes, it can be hard to predict how well patients will do based just on their Gleason scores alone.
- For example, your tumor may be assigned a Gleason score of 7 if the two most common grades were 3 and 4.The 7 may come either from adding 3 + 4 or from adding 4 + 3.
- Overall, someone with a Gleason score of 7 that comes from adding 3 + 4 is felt to have a less aggressive cancer than someone with a Gleason score of 7 that comes from adding 4 + 3. That is because the person with a 4 + 3 =7 grade has more grade 4 cells than grade 3 cells. Grade 4 cells are more abnormal and more likely to spread than grade 3 cells.
A new 5 Grade Group System has recently been created. This system does a better job of describing how a cancer will behave and respond to treatment.
- Grade group 1: Gleason score 6 or lower (low-grade cancer)
- Grade group 2: Gleason score 3 + 4 = 7 (medium-grade cancer)
- Grade group 3: Gleason score 4 + 3 = 7 (medium-grade cancer)
- Grade group 4: Gleason score 8 (high-grade cancer)
- Grade group 5: Gleason score 9 to 10 (high-grade cancer)
A lower group indicates a better chance for successful treatment than a higher group. A higher group means that more of the cancer cells look different from normal cells. A higher group also means that it is more likely that the tumor will spread aggressively.
Grading helps you and your doctor determine your treatment options, along with:
Prostate cancer-Gleason; Adenocarcinoma prostate-Gleason; Gleason score
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Gordetsky J, Epstein J. Grading of prostatic adenocarcinoma: current state and prognostic implications. Diagn Pathol. 2016;11:25. PMID: 26956509 www.ncbi.nlm.nih.gov/pubmed/26956509.
Pierorazio PM, Walsh PC, Partin AW, Epstein JI. Prognostic Gleason grade grouping: data based on the modified Gleason scoring system. BJU Int. 2013 May;111(5):753-760. PMID: 23464824 www.ncbi.nlm.nih.gov/pubmed/23464824.
Review Date 5/3/2016
Updated by: Todd Gersten, MD, Hematology/Oncology, Florida Cancer Specialists & Research Institute, Wellington, FL. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.