Also, I second what Krysalyss said about it maybe being an abcess, and pretty cheap for the surgery? My male cat got in a fight recently and a few days later I noticed he had a huge lump under his skin on his back - took him to the vet and they checked it out, found what looked like a puncture wound from a claw (which sounded right) and just lanced and drained it - cost me under $100 with antibiotics. About a year ago my female cat had a litter and then just after H was born, I noticed she was oozing yucky-coloured goo from her genitals... then she started growling and overgrooming and I realised she was in pain. Took her to the vet and they said she had a serious uterine infection and it was good I'd brought her in when I did or she would have died (within hours) I thought I'd be up for huge money as they had to put her under and give her a total hysterectomy, and it's more expensive when dealing with an advanced infection, but it was only a couple of hundred dollars... the vet was really nice and assumed I'd take the euthanasia option as money's tight, but when I heard it would only be a couple of hundred dollars I told him to take her out the back and do the surgery right now and I'd be back with DH's credit card within the hour. They said, 'Just pay when you pick her up' and threw in a course of a/b's for free... so I have my fingers crossed that your kitty's got an issue that *looks* bad but is easily solved!