diffrence about my two rats

Question
ok so i had a rat once when i was little and she had something like this too but it grew really big and it wad green. but it was really big to where i couldnt tell if it was over or under the skin but later the vet popped it and she had to stay overnight at the hospital.
but my now rat has just this flat but round bump that
i just noticed today and it moves wich ever way you poke it and it doenst hurt her so im pretty curious about my rat Lilly

Answer
What did you want to know about? What are you curious about, the flat round lump?  

What your other rat had was an abscess. The green was a nasty infection and that was the pus in it. This time it may be a tumor or a lipoma or even a sebaceous cyst. How long as she had this new lump?