Hi Steve
This stage of the diagnostic process is the most stressful. Once you know what you are dealing with it gets easier.
You're 68 so it would have been more of a surprise if you had not had prostate cancer. What is more important is how aggressive it is and until you have a biopsy and a Gleason score, we don't know. Many men live years with a harmless prostate cancer and die of something else.
A prostate size of 81cc is about two to three times average size, but that is of no concern, it is just a big prostate. It is slightly odd that you have been given the PSA density rather than the total PSA, however the density is the more useful figure.
Not having a calculator to hand in my head I calculate your PSA must be about 37 which divided by 81 gives 0.46 ; now a more normal figure for PSA density would be about 0.1 .
So I can see why the specialist thinks it is a high PSA density and presumably the MRI image showed something worth investigating.
We have had people on this site with higher PSA s than you and dodgy looking MRIs who have then been found to be all clear on biopsy. So you may get the all clear, but it is unlikely.
Until you get the biopsy results any idea of what you have got is guess work, and you may as well get Gypsy Rose to read your tea leaves. If I used loose leaf tea I would happily give you a diagnosis, but I use tea bags and I don't know how to read them.