I am going through this right now with Jaynie. Dental surgeon thought it was probably an epulis but took a small biopsy sample to be sure. She said they don't want to disturb it too much til they know what they are dealing with.
Should it turn out to be malignant there are various surgical options available depending on how invasive it is. If caught early, they can do a bone-sparing procedure that will remove some bone, but leave the bottom most line of bone. Otherwise they will remove a chunk of jaw.
While there are techniques under these circumstances to keep the jaw from drifting, it was her opinion most would not be optimal in a greyhound. The jaw would therefore drift somewhat, but apparently the dogs adjust quite well.
This was the gist of it - I am probably over-simplifying and in the process leaving out some important considerations.
We don't have Jaynie's biopsy results back yet, so I have no more detailed information.
All fingers and paws crossed here that Cooper has a simple epulis!