[OwnedByJezebel]

The cause of the swollen lymph nodes could most definitely be due to teeth/gum problems. If your dog needs a dental, that is MUCH more likely to be the cause than cancer. Did your Vet do an exam where they palpated other areas to see if they could find swollen glands elsewhere? If so, they probably didn't find any others affected except around the jaw, which led them to believe that the problem was an infection in the mouth.