Metastasis

Metastasis is a bad thing that happens to your body when some cells inside it decide to do something very bad. Normally, cells are very happy to stay where they are and help your body work the way it should. But sometimes, cells forget how to be good and they start to roam around your body, looking for somewhere else to go. When they find a place they can go, they try to take over and turn that place into a place where they can live. That's called metastasis, and it's bad because it can cause lots of different health problems.