Scary Thought

I was talking to a doctor friend of mine. The conversation was philosophical in nature. I had mentioned, Aristotle defined the highest good as that which is for its own sake (Being-for-self as Hegel might say). He replied: "that's funny, that's what I call cancer." Originally I laughed at this. On reflection, I'm frightened by the wisdom of that statement. Cancer is for its own sake...
What else is?