The cause of obesity. Your dog is over 40, almost 50 years old. It's time to keep him healthy. Ha ha. Be sure to go to the hospital to take a picture of the dog and see what is wrong with the bones of the spine, waist and legs. After taking photos, the hospital can still believe that D. lipoma is nothing serious. But it's a little big. Pay more attention to hygiene. Lipoma will fester one day. It would be better if it was superficial ulceration. If it is deep ulceration, you must see a doctor.