Without a lot of the specific detail, here are a few general comments:
Enlarged prostate symptoms, volume of cancer, and agressiveness of the cancer / gleason score, are not necessarily related.
Look at the recent posting here, "Small volume cancer PSA 20 G 8"
Someone can have a PV which is small in size, but it can still be an agressive cancer.
Determining the gleason score is a subjective process: a 2nd opinion can result in a different rating.