OBJECTIVE:Change in colon polyp size over time has not been well characterized. It has been inferred that some polyps will increase in size, leading to an increased risk of progressing to cancer, whereas other polyps may spontaneously regress. To develop a better understanding of the natural history of colon polyps, we prospectively investigated change in polyp size over a 2-yr period.

METHODS:Patients were enrolled if they had an endoscopically detected proximal rectal or sigmoid polyp measuring 3-9 mm. The index polyp site was then permanently marked with an adjacent India ink tattoo to allow definitive future localization of the polyp. Patients underwent flexible sigmoidoscopy at 6-month intervals, and at each examination, the polyp size was carefully measured with open biopsy forceps. After a maximum of 2 yr, each polyp was removed and the histology determined.

RESULTS:Thirty polyps were followed in 26 patients who completed the study. Twelve polyps were tubular adenomas (TA), one was tubulovillous, 14 were hyperplastic polyps (HP), two had no pathological diagnosis, and one was a leiomyoma. HP were more likely to decrease in size than were TA. Three polyps demonstrated fast growth rates (2-4 mm/yr), and all were TA. Two polyps were removed early because their size had reached 1 cm or more. Both of those polyps were TA. No polyps regressed completely during the 2 yr of the study; neither did we find consistent linear growth rates.

CONCLUSIONS:In contrast to prior reports, in this study, after polyps had been definitively localized with India ink, we observed no complete polyp regressions.