Grading prostate cancer

Grading describes how the cancer cells look compared to normal, healthy cells. Knowing the grade gives your healthcare team an idea of how quickly the cancer may be growing and how likely it is to spread. This helps them plan your treatment. The grade can also help the healthcare team predict future outcomes (your prognosis) and how the cancer might respond to treatment.

The Gleason classification system is most often used to grade prostate cancer. It is used for adenocarcinoma, which is the most common type of prostate cancer. The Gleason classification system looks at the differentiation of cancer cells and the pattern (arrangement) of the cancer cells in the prostate. Differentiation describes how different the cancer cells are.

To find out the grade of prostate cancer, the pathologist looks at tissue samples from the prostate under a microscope.

There are 5 patterns of prostate cancer cells based on their differentiation. The lower the pattern number, the more cancer cells look, act and are arranged like normal cells. The pathologist will give a grade for each pattern of prostate cancer cells found in the biopsy. The grade of the cancer corresponds to the pattern number. Gleason patterns 1 and 2 look a lot like normal cells. Gleason pattern 5 looks very abnormal compared to normal cells. Gleason patterns 3 and 4 are somewhere in between. Most prostate cancers have a Gleason pattern of 3, 4 or 5.

If the pathologist sees only 2 patterns of cancer cells, they will add the grades for each pattern together to get the total Gleason score. For example, if the pathologist gives the cancer cells in the most common pattern a grade of 3 and the cancer cells in the second most common pattern a grade of 4, the total Gleason score is 7. This is often written on the pathology report as 3 + 4 = 7 out of 10.

If there is a third pattern in the biopsy samples, the grade of the most common pattern of cancer cells is added to the pattern with the highest grade. This may be the second most common pattern or the least most common pattern. For example, if the pathologist gives the cancer cells in the most common pattern a grade of 3, the cancer cells in the second most common pattern a grade of 4, and another pattern of cancer cells a grade of 5, the total Gleason score is 8.

To make the Gleason score easier to understand, doctors developed the Grade Group system. This gives a single score from 1 to 5 based on increasing Gleason scores. For example, Grade Group 1 corresponds to a Gleason score of 6 and Grade Group 5 corresponds to a Gleason score of 9 or 10.

The Gleason score and Grade Group are described in the following table.