Maybe about 2-3 weeks ago I discovered a lump on one of my rat’s upper stomach and thought nothing of it, but it’s gotta bigger/longer? The first time I noticed it, it looked like a nipple, but now I’m more concerned because it’s grown! Does anyone know if this is a health problem?! Sorry the...

Today I found a lump behind the right front leg of my 15 month old female rat. Its flat and circular, around the size of a dime. She is acting normal but she is my first rat so I don't know what normal is. Since she is my first rat i am freaking out! HELP!