German Sheppard with Huge Arm/Elbow

Hello. Thank you for reviewing my post. I am new here and am posting for the first time. I have a German Sheppard (Roger). His left arm/elbow became large over the past couple of months. I took him to the Vet and they said they had no idea...took x-rays and said no tumor or cancer so they needed to do an exploratory procedure to try and determine the cause and if it is treatable. I did not have the $$$ at that second but am about to....so I am looking to get another view on the issue before I spend the $$$ on the procedure. She was a younger vet but I am assume they collaborated and had a mentor at the clinic.... *Roger can eat fine, drinks fine, hops around to go to the bathroom but that's it..... I included a pic but he is a little furry.....left side swollen. Huge hard ball of elbow....rock hard. Does not seem to be painful when touched but he is lame. Thank you for the time. SRD

Hello and I'm sorry to see your dog's leg looking so uncomfortable.  I am pleased to read that you have picked up on limping being a sign of pain and wonder whether Roger is on pain meds at the moment.   X-rays can indeed move bone cancer considerably down the list of differentials (ie make that possible cause of a symptom less likely) although I do wonder about other cancers (or possibly inflammatory processes), most of which wouldn't show on a leg x-ray, blocking the lymphatic flow out of the leg.   I wonder what your vets plan is from here?  Good questions for them include, What differentials haven't been ruled out yet?  What is the prognosis associated with these problems and what options they have moving forwards.