Seriously, read wikipedia or something. But if you put it this way, well, here is an internally caused dicease that causes your mind to attack and kill your own body by defenestration, d'ohCancer cells are your immune system attacking your own body, lolpwns your immune system. I.e. Tricks it into killing itself.
well, alzheimer's and parkinson's aren't caused by evil forces either. i wonder why nobody in this thread tagged them so far with allegations of non-sickness.depression is not some special snowflake disease caused by evil forces