The Gleason score plays a major role in helping patients who have been diagnosed with prostate cancer determine their outlook and treatment plan.
After a doctor diagnoses prostate cancer, a biopsy of the cancer cells in the prostate will be done. The Gleason score is then used by the doctor to help explain the results, determine how aggressive the cancer is and to plan the best course of treatment.
What is a Gleason score?
The Gleason score is a grading system devised in the 1960s by a pathologist called Donald Gleason and it measures the progress of a cancer call from normal to tumorous.
Five decades ago Mr. Gleason discovered that cancerous cells fall into five different patterns; these patterns change from normal cells to tumorous cells. He determined that these patterns they could be scored on a scale of 1 to 5.
Low Gleason scores
Cells that score a 1 or 2 look similar to normal cells and are considered to be low-grade tumor cells.
High Gleason scores
Cells that score closest to 5 are considered high-grade. These have mutated so much that, in comparison to the low grade cells, they have mutated so much that they no longer look like normal cells.
How is the Gleason score worked out?
The results of a biopsy are used to determine the Gleason score. During a biopsy, the doctor takes tissue samples from different areas of the prostate. Because cancer is not always present in all parts of the prostate, several samples are taken.
Using a microscope to examine the samples, the doctor finds the two areas that have the most cancer cells and assigns the Gleason score to each of these separate areas. Each sample area is given a score of between 1 and 5. The scores are added together to give a combined score, often referred to as the Gleason sum. In most cases, the Gleason score is based on the two areas described above that make up most of the cancerous tissue. However, there are some exceptions to the way scores are worked out.
When a biopsy sample has either a great deal of high-grade cancer cells or shows three different types of grades, the Gleason score is then modified to reflect the prediction of how aggressive the cancer will be.
What do the results mean?
When a doctor tells a patient their Gleason score, it will be between 2 and 10. Although it is not always the case, generally the higher the score, the more aggressive the cancer tends to be. Typically, lower scores indicate less aggressive cancers.
In most cases, scores range between 6 and 10. When biopsy samples score 1 or 2 they are generally not used because they are not usually the predominant areas of cancer.
A Gleason score of 6 is usually the lowest score possible. Prostate cancer with a score of 6 is generally described as well-differentiated or low-grade. This indicates that the cancer is more likely to grow and spread slowly.
Scores between 8 and 10 are referred to as poorly differentiated or high-grade, and in these cases, the cancer is predicted to spread and grow quickly.
In some cases, a patient may receive multiple Gleason scores because the grade may vary between samples within the same tumor or between two or more tumors. In these instances, the doctor is likely to use the highest score as the guide for treatment.