Alright that was just stupid. A CPU-measuring-computer-tumour? Why? And it's kind of unrealistic because tumours can't shrink and grow at such velocities.
Plus... putting it inside the case doesn't make much sense... how about OUTSIDE of the case? If that thing grows too large, it'll collide with the fans and circuit boards which if hot enough, could catch that rubber sack on fire. All they would have to do is cut a tiny hole for the air pipe and put the side of the case back on.
Zalman has a cool little module that shows CPU usage on a screen.