Lump PLZ help

Question
I just got home from a trip and I was feeding my rat when I saw a huge lump on her shoulder and was wondering what it is. She is going to the vet in a week(earliest appointment I could get.) It is hard like a rock and pretty big. can anyone help?

Answer
Might be a tumor, or it could be an abcess. My guess is probably a tumor, but I'm no vet. Either one can be treated by a vet fairly easily provided the situation is ideal (there are always unexpected things). I'm glad you have a vet appointment set up for her. I hope things go well!