Question: what is cancer?

Joe Bathelt answered on 12 Nov 2016:

Our body consists of little building blocks called cells. In order for the body to function properly, cells need to multiply to create new cells that replace old ones. This process is usually tightly regulated so that old cells die and not too many new cells are created. But sometimes something goes wrong and cells stop responding to the signals. If that happens, cells grow uncontrollably and even take over the place of other cells, which causes problems.