Oh, as an afterthought, I thought I should mention that the vet I went to did not in fact do the whole diagnostic series of tests to determine that it was in fact a salivary gland cyst. He looked at it, knew immediately what it was and recommended it come out. I looked online and saw that an MRI was in fact the only way to conclusively determine this diagnosis (as mentioned earlier); however, I made the personal decision that whatever it was, it needed to come off. I didn't care if it was a tumor, a cyst, or an abscessed tooth. As far as I was concerned it had to come out, so I didn't have the full series of diagnostics. The confidence my vet had (he said he'd seen it pretty often, and performed the surgery on a somewhat regular basis) led me to make this decision which did save me money in the end too. If you don't have a vet you really trust, and you have the money, go ahead and have tests done, of course.

Good luck