The Gleason Score Demystified


"If you are looking about information about Prostate cancer for yourself or someone you love, you are going to encounter the Gleason Score. OK so what is it? At it’s simplest the Gleason score is a measure of how aggressive or nonaggressive a prostate cancer tumor is. 

How is the score derived?  Again a simple answer. A medical professional, a pathologist, visually examines a biopsy sample under a microscope and makes a judgement based on what he or she sees there. We’ll come back to biopsies in a couple of minutes so stick around.

The biopsy sample, called a core, is removed from the prostate using a hollow needle. The pathologist examines the core and assigns scores from 1 to 5 based on how disorganized, irregular and ...well... just how messy things look.

A good general definition of cancer is “An abnormal growth of cells which tend to proliferate in an uncontrolled way...” And that’s exactly what the pathologist is looking for... abnormal growth and uncontrolled proliferation.

A Gleason 1 looks pretty much like the normal prostate glands and it represents a very slow growing non-aggressive from of the cancer almost a non-cancer

A 2 shows more space between glands and a little irregularity but still very slow growing

So here’s what 3 looks like. It’s an intermediate form of the cancer but still not very aggressive

Now 4...

and now 5. These last two represent the most aggressive form of the cancer

So the pathologist examines the core and assigns a score to any cancer he or she sees.  Typically there are two scores per core, the first or primary score represents the most prevalent form of cancer and the second, the less prevalent form.

That’s why you’ll hear or read things like Gleason 6, 3 +3. Or Gleason 9, 4 +5. 

Here’s where it gets a little tricky. A Gleason 7 does not always equal a Gleason 7. The order of the two scores is important. A 4+3 7 can be very different than a 3+4 7. The first, the 4+3,  is likely to require fairly dramatic treatment because the cancer cells graded 4 are most prevalent. The 3+4 7 might be best handled with ongoing observation... what we call “active surveillance” because the less aggressive cancer is most prevalent.

In general a Gleason score of 6 or less or a 3+4 7 are going to require active surveillance and a 4+3 7 and scores above 8 are going to require some form of hormone therapy, radiation, surgery or chemotherapy. 

So that’s the Gleason score...not that complicated. What we have to turn to now is the biopsy and how it came to happen in the first place.

Up until recently here was the typical sequence of events.

A man would get results from his yearly PSA test that were higher than usual. Typically that would mean a number of 4 or greater.

His GP would refer him to a Urologist who would almost immediately perform a random needle biopsy which entails removing 12 cores from the prostate. 

Those cores would be sent to the Pathologist who would examine them as we described earlier.

There’s a real problem here. Using this sequence an estimated 80% of men get biopsies that they don’t need! 3% of those suffer infections serious enough to require hospitalization not to mention other side effects like erectile dysfunction. Oh yeah, one more thing... random needle biopsies are not terribly accurate. They can miss serious cancers.

Thankfully things have changed and nobody needs to be railroaded into the random needle biopsy. If you or your loved one has a high PSA number here’s a better sequence:

First get a second PSA test. Labs can make mistakes and PSA can be elevated for reasons other than cancer.

If the PSA number is still high you have options to see if a biopsy is a good idea:
First an MRI. Recent advances in MRI  imaging has changed everything. The latest generation of MRI machines called 3 Tesla, or 3T machines enable radiologists to see all but the tiniest tumors. The tumors that they can’t see almost certainly don’t matter. You can find  a list of MRI centers that do “Multi-parametric” testing using a 3T scanner on

The second option is a new blood test called the 4K test that can tell with a high degree of certainty whether you have an aggressive form of the cancer. You can read about the test here (where?). If the test indicates that you may have an aggressive form of the cancer then you’ll want to move to the MRI

What improvements in MRI imaging mean is that biopsies, when they are needed, can be targeted, right to the suspicious area in the prostate. No more random poking. 

Be warned though, many doctors are still following the old sequence that involves the random needle biopsy. Exercise your options. You may have to look for a more forward thinking doctor but avoiding the risks is worth the trouble.

Finally, even if the tests all show that you or your loved one has more aggressive prostate cancer, always remember that in the vast majority of cases it’s a very slow growing cancer and you have time. Take a deep breath. Do your research. Understand the side effects and implications of any treatment that you may undergo. is a great resource for you. Explore the site. If you can’t find the answers you need, call the Helpline.

It’s your health. Take control of it."