Caner is our own cells that proliferate rapidly and without being checked. Our immune system does not recognize our own cells as a threat. Usually our immune system attacks foreign bodies. Thats why we have to find a match when performing organ transplants. Even when it comes to cancer markers, these markers are produced all the time in our bodies but the over produce when we have cancer and thats how we diagnose if we have cancer by use these values.
Cancer has been around for many years, It's just that we are recently finding ways of diagnosing it.

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