The fight against colorectal cancer, by most accounts, is going well. With colonoscopy, doctors can prevent most of these malignancies by detecting and removing polyps, growths along the colon that can be precancerous. But some people who have had polyps removed or who have gotten a clean checkup still get diagnosed as having colorectal cancer a few years later.
A new study suggests that these out-of-the-blue cancers may arise from nonpolyp growths. Such tissues are less conspicuous than polyps, but the new data suggest that they occur with some regularity and might be more dangerous than polyps.