If it's not something simple like an abcess, I would ask for a referral to a veterinary dentist. They are few and far between but are the specialists. They might have a better chance of removing it without taking out teeth.
Leigh, if this is malignant, or even an aggressively growing "benign" tumor, the last thing you want to worry about is saving Loki's teeth. You will be focused on saving Loki's life. If this is malignant or aggressively benign, odds are he will need not only teeth but a piece of his jaw removed. A friend of mine had a Lab who had to have one quarter of his lower jaw removed because of an aggressive "benign" tumor. He did great, the tumor never came back, and he lived to be 12 years old. And the dog and his owner couldn't have cared less about his missing teeth.
They will probably want to take an xray to get an idea of what it might be. Will start him on antibiotics. Possibly prednisone.
Leigh, unless you know for sure what this is--and this requires a fine needle aspirate and/or a biopsy--you do not waste time with antibiotics or prednisone. If this is malignant or aggressively benign, getting it totally removed as soon as possible is critical.
They can do a needle aspirate but I usually choose to not do that in case a growth is something like a mast cell. A needle aspirate would cause an inflammatory response (as the body is designed to do in an injury) and can make a MCT worse.
A fine needle aspirate is especially important to do if a mast cell tumor is suspected. If it shows that the mass is a mast cell tumor, that gives the surgeon a critical piece of information--he or she needs to take very wide margins, and the mass should be removed as soon as possible.
I learned this the hard way when a dog of mine developed a little bump that looked like a mosquito bite. The vet refused to do a fine needle aspirate before the surgery and did not take wide margins. The mass and surrounding tissue were sent to a pathologist and found to be a mast cell tumor with dirty margins (cancer at the edges of the surrounding tissue). So the poor dog had to have a second surgery to totally get rid of the cancer. The cancer never came back and he lived to be 15 years old. I never let that dingbat vet treat any of my dogs again.
When another dog of mine developed a mass, I insisted on a fine needle aspirate, which showed that the tumor was a fibrosarcoma, a very nasty, aggressive cancer. This told the surgeon that he needed to operate immediately and take wide margins, which he did and got it all. The tumor never came back and the dog lived to be 14.
Leigh, you are going to hear lots of conflicting advice about Loki. You are an intelligent person with common sense, but your understandable worry and distress may cause you to be whipsawed back and forth. For Loki's sake, you need to stay as calm as you can and use your brains and common sense. The basic principles for dealing with something like this are straightforward:
1. Get a diagnosis as soon as possible. This means a fine needle aspirate and/or biopsy. X-rays may be needed to see if the mass has spread to the bone, but they are
not enough by themselves.
2. If the mass needs to come out, have it done as soon as possible by a good board-certified vet surgeon, not a GP or dentist. You may also need to consult a board-certified veterinary oncologist.
Hang in there! Even if Loki's mass is something horrible, it may be totally treatable and he could live a long life
if he is diagnosed quickly and treated promptly and correctly. So please don't panic, and use your head when evaluating advice.