My rat has developed a tumor on both sides of his neck. This developed rapidly. There are 2 other obviously benign encapsalated tumors on the side of his abdomen that also seem to have come up rapidly. But the severe swelling around his neck is what bothers me. Yes I took him to the rat vet who says its probably lymphoma. She has been wrong before. He is on clavamox now and she also prescribed prednisone. Seems to be okay, eating, eliminating, sleeps more. Has anyone had experience with this.