I've recently started noticing growths on two of my girls. My vet thinks that they're tumors, and that there's nothing we can do that would improve quality of life. I'm propably grasping at straws here, but is there anything else that could cause lumps to grow on a rat? The two are half sisters; could they have inherited some wierd genetic condition from their dad? It just seems odd to me that the growth on the younger is the same size that the older sister's growth was when we noticed it two weeks ago (their litters were born about two weeks apart). On both of them the lumps are located on the underside of their bellies near the anus.