Flat elevated lesions with neoplastic potential can occur in the colon. The detection rate is greatly improved with new endoscopic techniques. Magnifying chromoendoscopy allows frequently a real time diagnosis, based on the pit pattern. Not all flat elevated lesions are adenomas. Small sessile serrated adenomas can mimick flat adenomas. Diagnosis of this lesion thus far implies histology because the pit pattern can mimick that of hyperplastic polyps. Rare non neoplastic lesions can also present as a flat lesion. Flat adenomas comprise from 6.8% to 44.4% of all colorectal adenomas. The exact neoplastic potential of "flat adenomas" remains unclear. A subtype with central depression may be associated with more high-grade dysplasia although the depression may not be a specific diagnostic sign. Studies looking for gene expression profiles demonstrate differences between flat adenomas and normal colon mucosa but confirmation is needed. Early detection, removal and more close follow up (in patients with advanced histology) are indicated.
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