Question: How is a cell with someone with cancer different to someone without cancer?

Ee Lyn Lim answered on 21 Jun 2013:

Simply put, cancer cells are cells that grow out of control.

Normal cells in your body are nice and obedient – they only grow where they should (so you don’t get an ear in the middle of your back), they only grow WHEN they should (girls only grow breasts during puberty), and they will die when they become damaged, or when you don’t need them anymore (skin cells at the surface die all the time and form a protective layer all around you). They do all this because their DNA tells them to – it’s like a set of instructions that tells cells how to behave.

Sometimes the DNA gets damaged, for any number of reasons – UV rays from the sun can break it, or harmful chemicals (for example cigarette smoke) can change it, or some virus infections can change it too. Then the instructions are broken, and the cells go out of control. They won’t stop growing and dividing and multiplying, so you get a lump of cells that shouldn’t be there – that’s what a tumour is. They’ll keep on growing even if they’re crowding and pushing other organs in your body, which is why cancer is painful and can kill you. And they won’t listen when they’re told to die – there are proteins in cells that act like guards, and if there’s something wrong with the cell they ought to stop it growing and make it die. But cancer cells don’t pay any attention to their guards (a lot of the time the guards are broken, because of the DNA mutations) and keep going, no matter how damaged they are.

That’s why cancer grows so quickly, and can spread to other parts of the body too. It’s only cells in the tumour that are like that though – someone who has cancer also has normal cells like you or I, in the other parts of the body that aren’t affected by the cancer.