Chinchilla Cancer?

So I have a friend who has had two chinchillas that have died from cancer (she has a new one now). These chinchillas were not related, not the same age, and she didn't even have them at the same time, but they both got cancer in the jaw. This she knows because she took them to a vet and the vet diagnosed it saying it was probably hereditary, but that isn't really possible. (I own the mother of one of the chinchillas) I'm wondering if it could be something in the cage or room, that's the only constant factor. It's a big cage (metal with tight mesh floors) it has plenty of bird toys, a wheel, a little chewing log, etc. What could have caused this? Has anyone else ever heard of an occurrence like this? Thank you.