I dealt with the cancer scare in June. Tango (8 years old) had a mast cell tumor on his side. It was a grade 2 out of 4 grades. Luckily, the surgery was successful and he is now in remission. If he had needed chemotherapy, I would have set down with the vet and made a pros and cons list of chemotherapy. Is it worth it? Will he be in pain? What is the cure rate? etc. I wish you the best of luck, I'm hear if you need to talk.