Burst Guinea Pig Tumor

Question
I have a guinea pig named Jasmine that is about 1.5 years old. As of recently a large lump on her hindquarters, positioned where a tail would normally be, has burst. The lump is pretty much the size of a mini donut, the inside containing a white porous material as well as red, fatty tissue. My vet offered a personal opinion as to what said lump might be and believed it to be a tumor rather than a cyst or an abscess, though no tests were run. With this opinion he perscribed an antibiotic,"Baytril," which I have been giving her daily, to little affect as far as shrinking the lump, though the opening has appeared to have moved to the right from its previously symmetrical position. As of now, my guinea pig's "tumor" bleeds occasionally with her constant picking and has also developed an extreme thirst, though no other negative symptoms are apparent. As we cannot afford surgery to remove this troublesome lump, especially in the case where it would do her little good, I am simply asking another opinion as to what this appendage might be, and if possible, ways to keep her comfortable and her wound clean.

Answer
Hello Melissa,
if you haven't already I'd try using some soft bedding like carefresh or soft-sorbent bedding. If the guinea pig thought it was a tumor I wonder why he would use Baytril. I honestly couldn't tell you whether it was a tumor, cyst or abscess without tests. The best thing you can do though is to try to keep the area clean with mild soap and water and I'd try to apply some neosporin to the area to keep it from getting an infectoin.