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 is less aggressive.

Prostate cancer - Gleason; Adenocarcinoma prostate - Gleason; Gleason grade; Gleason score; Gleason group; Prostate cancer - 5 grade group

The first step in determining the Gleason grade is to determine the Gleason score.

• When looking at cells under the microscope, the doctor (pathologist) assigns a number (or grade) to the prostate cancer cells from 1 to 5.
• This grade is based on how abnormal the cells appear. Grade 1 means that the cells look almost 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 3. Grades below 3 show normal to near normal cells. Most cancers have a Gleason score (the sum of the two most common grades) of 6 (Gleason scores of 3+3) or 7 (Gleason scores of 3+4 or 4+3).

Sometimes, it can be hard to predict how well people 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 5 Grade Group System was created to have a better way to describe 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 health care provider determine your treatment options, along with:

• Stage of the cancer, which shows how much the cancer has spread
• PSA test result
• Your overall health
• Your desire to have surgery, radiation, or hormone medicines, or no treatment at all

Bostwick DG, Cheng L. Neoplasms of the prostate. In: Cheng L, MacLennan GT, Bostwick DG, eds. Urologic Surgical Pathology. 4th ed. Philadelphia, PA: Elsevier; 2020:chap 9.

Epstein JI. Pathology of prostatic neoplasia. In: Partin AW, Dmochowski RR, Kavoussi LR, Peters CA, eds. Campbell-Walsh-Wein Urology. 12th ed. Philadelphia, PA: Elsevier; 2021:chap 151.

National Cancer Institute website. Prostate cancer treatment (PDQ) health professional version. www.cancer.gov/types/prostate/hp/prostate-treatment-pdq. Updated March 11, 2024. Accessed May 30, 2024.