I pray that it is not the dreaded "C" word. Just a thought, my boy Beau that passed away this year had a large lump that was about the size of a baseball. It was on his shoulder area under the skin and caused him to limp. The vet removed it not sure of what it was, it came back to be a normal fatty tumor. He had some all his life but that one was huge and was messing with the muscle. Not saying that is what your pup has but you never know.
I would get the surgery done to see what it is and go from there. My toughts and prayers will be with you on Friday.
I would get the surgery done to see what it is and go from there. My toughts and prayers will be with you on Friday.