Question: What does cancer actually do? we hear its deadly, but no one has told us what it does.

Greg Melia answered on 7 Mar 2016:

Now that is a really good question.

Cancer isn’t a disease like flu or cold, where external viruses or bacteria come in and infect the body. Cancer is where our own cells start reproducing themselves uncontrollably.

Our bodies are made up of billions of cells, each of which has a central part (the nucleus) that contains a copy of our DNA, which is the ‘code’ that has all the instructions about how our bodies are built. All our cells eventually die, so some of our cells reproduce themselves to create new cells to replace the old ones.

When someone gets cancer, some of our cells go out of control and start reproducing at very high speed. This is usually because their DNA has been damaged somehow, so the instructions now tell them to do this. The person gets a big lump of cancerous tissue growing in them. In later stages, the cancer can spread, so the person gets cancers growing in them in several places. Lots of the person’s energy is then going into growing pointless new lumps of cells, and the cancers themselves can really disrupt how those parts of the person’s body work. Think about having a big lump of cancer growing in your brain and squishing the rest of your brain against your skull – I hope you can see how that would be bad news!