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Colorectal Cancer Health Center

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Flat Lesions Linked to Colon Cancer

Flat Lesions Can Be Overlooked During Colonoscopies
WebMD Health News
Reviewed by Louise Chang, MD

March 6, 2008 -- They are usually missed or overlooked during colon cancer screening, but flat lesions within the lining of the colon and rectum may be more likely to be cancerous than polyps, new research shows.

They are also more common in the U.S. population than previously thought.

Known as nonpolypoid colorectal neoplasms, they were found in roughly 9% of patients who underwent colonoscopy in the new study, published in today's edition of The Journal of the American Medical Association.

And the flat lesions were roughly five times more likely to contain cancerous tissue than polyps, after adjusting for polyp size.

"This study shows that flat lesions are actually a lot more dangerous than protruding ones," researcher Roy M. Soetikno, MD, tells WebMD. "We can do a better job of preventing colon cancer if we look for them, but this will require that the patient and the doctor work together."

Spotting Flat Lesions

The flat or even recessed lesions are much more difficult to spot than raised polyps with traditional colonoscopy, because their appearance is similar to normal tissue.

Soetikno says patients can help by doing everything their doctor recommends to prepare for a colonoscopy. The lesions are even harder to spot if any waste is left in the bowel.

And doctors must be made aware of the importance of the nonpolyp lesions, and do a thorough job of looking for them.

In the study, Soetikno and colleagues using a special dye to highlight subtle changes seen with standard high-resolution colonoscopy.

This takes much longer than a standard colonoscopy, but it is an important step, Soetikno says.

New-generation endoscopes don't require the dye step, and they may be able to detect the lesions more accurately and quickly than older endoscopes.

Studies suggest that about one in four colonoscopies are compromised by poor bowel cleanout.

"You can't overstate the importance of the prep for a good-quality exam," American Society for Gastrointestinal Endoscopy President Grace Elta, MD, tells WebMD. "You hear over and over that the prep is the worst part, but it is also the most important part."

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