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Asked by Imo to Chris, Josh, Rebecca, Rob, Susan on 15 Jun 2015.
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Rebecca Dewey answered on 15 Jun 2015:
I don’t think that everyone has a tiny percent of cancer in them, I’m not sure where you heard that.
So cancer is where cells grow abnormally in the body and can spread to other areas of the body. This can eventually stop an organ from functioning properly (such as liver or pancreatic cancer) or can take up precious space (such as brain cancer). Cancers occur purely by random and there’s not many things that are absolutely guaranteed to start cells growing abnormally. Cells start becoming abnormal purely by chance and everyone has a tiny percent of a *CHANCE OF DEVELOPING* cancer – is this what you meant? Mostly your chance of developing cancer is inherited from your mother and father, your genetic make-up. Certain things increase that chance, such as being exposed to carcinogens (cancer-causing chemicals such as smoke, radiation, asbestos, charred foods). In the other direction, some things can DECREASE that chance, such as keeping a healthy lifestyle, and a healthy weight, exercising, eating healthily and in some individuals, taking medication or vaccinations.
So your personal percentage chance depends a little bit on your diet, a little bit on the amount of exercise you take, a little bit on the air you breathe, etc. etc, and quite a lot on what genes your parents have passed on to you. You can keep your chance as low as possible by being healthy!
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Josh Meyers answered on 15 Jun 2015:
This is actually true!
Cancer can be classified as malignant (aggressive with the potential to progress and grow) or benign (unable to invade neighbouring cells and grow).
The average human may have many benign tumours. These are usually found on the skin (that we know of…) and are usually harmless and very common. Many moles are actually benign growths (nothing to worry about!)
As for how much we have got. A very very very small amount.
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Susan Cartwright answered on 15 Jun 2015:
I wonder if you’ve got confused between cancerous cells and mutated cells?
Cancers are caused when the genetic code of cells is damaged such that they begin to reproduce abnormally – more precisely, the control that usually governs when cells divide and when they die goes seriously wrong, and the cell line proliferates out of control. This loss of control is caused by mutations in the cell’s DNA that affect the relevant mechanism. Sometimes these mutations can be inherited, like the mutations that cause some types of breast cancer, but more often they arise spontaneously during your lifetime. This is why exposure to things that are known to cause DNA damage, such as excessive sunlight, some chemicals, and radioactivity, increases your risk of developing cancer.
Everybody definitely has some mutated cells. I found a paper which said “Assuming 1.5% coding DNA, these somatic rates roughly translate into approximately 100 to 1,000 mutations per nonreplicating diploid cell at the age of maturity and approximately 1000 to 10000 per replicating cell.” Yes, that does say 100 to 1000 mutations in every cell in your body. HOWEVER, most of these mutations are harmless, or at least just affect the functioning of that individual cell – very few of them cause the cell to become cancerous.
This is not enough to protect us from cancer. Humans are large, long-lived animals: even rare cancer-causing mutations would be too much. Consequently, humans have a number of “tumour suppressor genes”, which prevent cells with potentially cancerous mutations from developing into cancers. It appears that for a cell to become cancerous, it both needs a mutation that would predispose it to cancerous growth, and a mutation that knocks out the relevant tumour suppressor gene. So it is quite likely that everyone does have some cells that have potentially cancerous mutations, being firmly held in check by working tumour suppressors. As for the exact numbers, I’m afraid I don’t have a clue – I’m not an oncologist!
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