My lab has a recurring lump on her side. We know its coming because she is lethargic with a fever. Acts pitiful and within 2 or 3 days the lump appears in the same spot....until it burst. A pick discharge comes out and then she is fine until it happens again. This has happened twice. The first time the lump appeared the vet did all sorts of test for cancer, etc and all came back negative. They at that time couldn't tell us anything so we put her on pain meds and an antiobotic. Any clue what this is?