Hi Pamela!
I'm not an expert in herbal veterinary or cat care, so I can't fully answer this question. I know that we need to be extra careful with topical applications for cats because cats tend to lick them off, so anything you use topically needs to be safe for the cat to consume internally. I don't know which herbs are safe for cats to consume internally.
If this were a human, I would suggest a salve made from poke root, with potentially violet leaf and calendula. Poke is the best topical oil for tumors, but it is also a low-dose botanical and can be an emetic in even moderate doses. I truly don't know if poke is safe for cats.
I know that there are a few vets among the alumni; they might be a good resource. I've also heard that Juliette de Baircli Levy's books are helpful, though I bet there are newer books that have been published.
Good luck,
Amanda