My iguana has cancer, what should I do?

My iguana that I have had for about two years has just been diagnosed with cancer. It looks like a huge pimple on the side of his face that goes all the way from his eye to his mouth and the cancer has now spread to his mouth. The large ball is now pressing against his throat which is making it hard for him to eat and stuff. Its my brother's iguana but he is not around at the time and I don't have the guts to tell him about his iguana. Should I have the Iguana put down? What should i do? Help!