For example, if someone discovers they have breast cancer or cancer in the liver or something, does that mean that they always had cancer but it was not able to be detected until they discovered they had it? Or is that something that is formed later, and wasn’t always in that person’s body?
In: Biology
No, they didn’t always have cancer. It happened later. (Though many types of cancer don’t start generating symptoms and getting noticed until *years* after the person gets them.)
There are several different mutations that have to happen for tissue to become cancerous: it has to deactivate the gene for “only grow when needed”, deactivate the gene for “self-destruct if you notice yourself growing out of control”, activate the gene for “don’t age”, and a couple others that I forget.
The tissue itself—the breast, liver, or whatever—will have been present all along, and sometimes one of the mutations will have been there all along too (there’s a gene that famously raises women’s chances of getting breast cancer from like 5% to 50%, because it gives their breasts a head start to turning into cancer), but the other mutations happen as a result of the tissue being damaged and repairing itself incorrectly.
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