We took her to the vet today. It's some type of cyst, but not a histiocytoma in the sense that it won't go away by itself. Sooooo, we have to make another appointment to surgically remove the cyst and she'll be fine It is in an area with little extra skin, so they'll probably have to keep her for two nights.

I'm not sure which will be more stressful - making the appointment or handing Ivy over for two nights