"My dog has a tumor that has just popped up on ... Osteosarcoma: This can be external, just on the jaw bone, and not involve the mouth at all. Without having the tumor aspirated and the cells ...

Some of the possible causes of a tumor in a dog's mouth or on the jaw include the following: Osteosarcoma: This can be external, just on the jaw bone, and not involve the mouth at all. Without ...