Quote (Ratatatatat @ Jun 15 2011 02:21am)
a couple days ago we noticed a lump on my dogs back leg that was not there a few hours previous. it is about the size of a ping pong ball. its strange that it appeared so fast
well my dad took her to the vet today and he said its cancer

what do i do
I'm sorry to hear that
I can't tell you what to do. There are options. You could try to treat it, or save your dog a vast amount of pain and put him to sleep. There are numerous options, and I can't tell you which one is right for you. You may wish to talk to your vet further on this.