The size of colon polyps revisited: intra- and inter-observer variations.

BACKGROUND It has been postulated that the occurrence of invasive carcinoma in a colon adenoma can be predicted by estimating the size of the resected polyp. Recently, significant intra- and inter-observer differences in size were found when 22 pathologists estimated the size of 12 polyp phantoms. In this work, the size of a large cohort of endoscopically-resected colon polyps was assessed with a novel method. PATIENTS AND METHODS Three pathologists measured photocopies of 148 resected polyps (adenomas at histology) in two independent trials. RESULTS The size recorded by the three participants was congruent in only 50% of the measurements in trial 1, and in 62% in trial 2. A significant difference in size assessment was found between the three investigators (p<or=0.05). When 6 possible combinations (the 3 size limits proposed for predicting cancer risk in adenomas, and 2 different trials) were tested for the 13 adenomas showing invasive carcinoma, merely one of the three participants recorded the same size, but only in 11% of the 6 possible combinations. CONCLUSION Present and previous investigations indicate that the lack of reproducibility makes the use of size limits in predicting cancer risk in polyps removed at colonoscopy unreliable.