Natural history of small colorectal protuberant adenomas.

Most previous studies of the natural history of small colorectal adenomas showed no increase in size, no changes that would have necessitated treatment within a couple of years and that malignant transformation is rare. Using endoscopic follow up for a mean period of 43.1 months we assessed the development and progression of 408 protuberant adenomas that were under 10 mm in diameter. Of the 408 lesions, 22 (5.4%) underwent morphological changes. There were 12 lesions (2.9%) whose final tumor diameter had reached 10 mm or more. There were three lesions (0.7%) that developed and progressed into intramucosal cancer. We concluded from the literature and from our own results that small colorectal protuberant adenomas do not grow to advanced adenomas within 5 years.