system
Given the following post, respond as if you're commenting on Reddit:
human
Why is leukemia the most common cancer amongst children?

is there something about the white blood cells in children that‘s more susceptible to cancer? just curious.
gpt
The big picture is that kids don't get cancer much at all, because their cells haven't had nearly as many chances to divide and accumulate errors as an older person. This doesn't leave many ways to get cancer, so the few that are left become "common." Leukemia makes up a third of childhood cancers partly because familiar types like colon/lung/breast/prostate cancer are next to nonexistent in kids. 

Bone marrow is full of tons of precursor cells that are constantly trying to make more cells, many of which go through multiple stages. Already a good setup for cancer because there's tons of copying and division. We make tons of red cells, but iron is a big limiting factor so they're less likely to get out of hand. White cells, on the other hand, are part of the immune response, which is to say our survival depends on the ability to ramp up production like crazy on a moment's notice. Very helpful, but it also means fewer brakes that have to fail until we start making way too much of one.