Imiquimod
"Our veterinary oncologist recommended this for our cat's carcinoma.  It looks like there may be some improvement, but the cream is HORRIBLY EXPENSIVE!!  It cost over $300 for 12 little packets that only have a few drops each.  Not only that but one packet was able to treat 2 small areas on our cat twice, then the next packet had barely enough to treat her once.  It seemed as though there was an air bubble inside like it didn't get filled properly."