Cancer cells pop up in everyone's body all the time, and your immune system is fighting them off on a regular basis. It becomes a problem when your body is either overwhelmed or these things come up so often that it no longer recognizes the threat.

If you don't want to run into the same problem, the absolute best thing you can do is to keep your body in the best shape possible. Physical exercise often, not overeating, getting an appropriate amount of rest.

Everyones' bodies are different and YMMV, but the tools to prevention are well known, they just sometimes don't coincide with people's chosen lifestyles.

You might want to also consider adding a little more olive oil to your food, and/or researching it more. It's really quite impressive.

Testing is invasive and expensive, and any part of your body could become cancerous. Would you like a colonoscopy twice a year? All your moles biopsied twice a year? Mammograms and MRI twice a year?

There is no way to make sure, nothing in life is "sure", especially not the random mutations that cause cancer.

Just eat healthy, exercise, enjoy life, and tell people you love them while you can.