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This question originally appeared on Quora. Answer by James Marshall.

Yes. Everyone gets cancer. In fact, if you are reading this, then technically you have had, or will have cancer, some time today. Let me explain.

Cancer is a failure of the biological mechanisms that govern the normal lifecycle of cells in your body. For a range of reasons, the biological mechanisms that govern cell division, cell growth and cell death occasionally go wrong, resulting in cells growing and dividing uncontrollably. Cancerous cells may take over normal cells in surrounding tissue or detach, enter the bloodstream and spread to other parts of the body. Uncontrolled cancerous cell growth can cause other complications in the body, which can ultimately result in death.

There are various failures that can take place in the otherwise normal biological processes of cell lifecycle that can result in cancer. For example, a cell may receive an incorrect biological message from other cells telling it to multiply, a cell may not divide properly or a cell may fail to die as it was biologically programmed to do. The underlying causes of these failures is damage to cell DNA, which can in turn be caused by a wide range of factors including old age, random mutations, viral damage, the presence of particular chemicals, exposure to particular radiation energy etc.

Every minute, millions of cells in your body die and are replaced by new cells. This process goes wrong in a very, very small percentage of the time each and every day. However, in the vast majority of instances, the body’s own immune system or the cells’s own programming recognizes the failure and destroys the affected cell before cancer can take hold. In this respect, we all get cancer every day, but it is nothing to worry about because our bodies are capable of dealing with it.

Occasionally the body's immune system fails to properly detect or manage these failures. For example, it may be that the form of cancer is such that the body does not recognize something has gone wrong; it may be that the damage is so widespread that the body’s immune system is overwhelmed or it may be that the body’s immune system is not working properly. When this happens, cancerous cells may take hold, resulting in a form of cancer disease.

So just to clarify, not everybody gets a cancerous disease, but everybody gets cancerous (or what are often referred to as pre-cancerous) damaged cells. Many people die from many other causes — including nothing more than old age — without experiencing a fully developed cancerous disease.

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