Question: How do you determine the difference between tumor cells from normal ones?

That’s a great question. We know that tumour cells behave in certain ways that are different to normal cells. They grow faster, often accumulate DNA mutations faster, and don’t respond to the signals (like hormones) that normal cells do. BUT, actually detecting that difference (especially in a living body) can be pretty tricky. The really hard thing to figure out (and what many scientists are working on) is trying to figure out what goes wrong in the first place to make a normal cell start behaving strangely.