Maggots

Don't read the article unless you have a strong stomach.
When I was in Africa, we had a patient with cancer of the face (sarcoma of the maxillary sinus) that was huge and fungating...and full of maggots.
We had to put him to sleep to clean them out...
Poor man...we kept him on lots of morphine until his cancer ate into his brain and he died of meningitis about a week later.
Most maggots only eat dead tissue, so sterile maggots are one treatment for severe non healing ulcers. But there are forms that eat and burrow into live tissue.