Is it possible to have normal stool with colon cancer?

Yes! Most colon Cancers may not show up in or effect your stool till it is late and quite advanced(enough to narrow or block the lumen of the colon. If there is sufficient risk of colon cancer, then Colonoscopy is the best way to check for Colon Cancer provided the person is 50 years or older( this is the age to begin screening for Colon cancer in an asymptomatic person).