In 2011-2012 what is. The estimated percentage of colon cancer awith someone in their 20s how worried should I be?

Extremely low. The incidence of colon cancer is very unusual or even rare under the age of 40. If there is an underlying condition such as colitis or familial polyposis, then the disease can occur very early. If there is a history of a very young person in your family that got colon cancer, then your risk is high enough to have a screening colonoscopy around the same age.
Very low. If you have no family history of colon cancer, and no symptoms at all, the percentage is extremely low. If any of the above apply, it is a different story.