Which answer would you like to hear? This is PCa, it usually is totally inconsistent, beyond normal rational analysis and thinking on almost every parameter you can mention. It is a wild world in effect.
S.W.A.G.~ the scientific wild ass guess is let's look at a what is PCa? Well it is said that there is atleast 18-19 variant types of PCa....so which one(s) are we talking about? Next out of those some of them are way different than the type most of us are diagnosed with, i.e. like squamous cell, signet ring or small cell and a few other 'radical' types (for lack of a better term) and they can be super aggressive in comparison.
Next parameter that probably has alot to do with 'possible' up staging/changing of Gleason pathology, is plodity analysis of the PCa cells DNA structures, i.e. how is it built. Three types exist and the first one is the closest to normal cell structures, called Diploid and has double stranded DNA and is the easiest to control with hormone therapies etc. it is said..thus (likely clue this is the safer of the 3), second one is aneuploid which has multiple stranded DNA's(repsonds not as well to hormone therapies) and third was tetraploid(or something like that...from memory right now..no quoting) and it has wild DNA structures and would be the worst prognostically. So the crazier the PCa cells DNA structures, the more wild it is.
This is why some pathologists offer "plodity" testings for additional $350 or such, Jon Epstein is not doing plodity analysis for whatever reasons, but among the experts on pathology, the other guys I mentioned in a posting, apparently all do ploidity. I am sure there are other reasons and parameters and maybe Tony or someone else can throw in some more information on this. Not saying I had the answer for you, but you can see how complex PCa can become.
It is possible to have low Gleason scores under 5 or 6, although it is somewhat uncommon and could be reviewed to make sure it was correct and not under graded, heard this from Bostwick himself at PCa support group.
"Youth is wasted on the Young" (W.C. Fields....ah yes)