Hi All--I have a six week old ameraucana pullet that has an enlarged right breast, like a big lump just to the right of the keel bone about the size of a third of a golf ball. It's firm like muscle, doesn't appear to be sensitive when pressed, it's fully feathered with no sign of a wound, and so on. Other than this malformity, she's in very good shape, about the third largest of the five clutch mates, good appetite, good energy, and so on. She's just very asymmetrical up front. The other four birds are fine. Thoughts? Could this be a tumor?