Question: How do people get cancer?

Jimi Wills answered on 14 Mar 2016:

Cancer happens because cells multiply out of control. Cells are the building blocks of our bodies. Cells can grow and divide, it’s called cell-division. Cells can make more cells by doing cell division. It’s necessary to replace dead cells, e.g. your blood cells are recycled about once every 3 months, and cells in your bone marrow make more blood cells.

But any cell can become a cancer cell. The problem starts with DNA damage. The DNA is the instructions for the cell. For example, the DNA tells the cell when it should and should not undergo cell division. Most of the time this is also dependent on messages coming from other cells and the rest of the body.

But when DNA is damaged, the instructions go wrong, and cells can start undergoing cell-division even when they shouldn’t. And then don’t listen to messages from other cells or the rest of the body telling them to stop. Once cells are dividing in this way we get a tumour – a mass of cells growing out of control. And that’s cancer.