system
Given the following post, respond as if you're commenting on Reddit:
human
Eli5: Why is cancer so harmful to the body?

I understand that cancer is uncontrolled reproduction of cells but why is that so harmful? How do extra cells make is so sick?
gpt
Tumors not just replicate, they actively siphon off the body’s resources by causing blood vessels to grow into them and provide them with nutrients. These blood vessels are what makes tumors look vaguely like crabs with veins protruding all around as if a lot of limbs, giving cancer its Latin name. With tumors spreading and growing everywhere the body eventually runs out of resources and dies.