[Adenoma-carcinoma sequence in the right colon].

Most endoscopically treated colorectal adenomas are found in the sigmoid colon and the incidence gradually diminishes in the proximal districts until we reach a figure of 10% or so in the right colon. The present series of 356 adenomas endoscopically removed in 1980-85 differs from other reports in that 24.4% of the adenomas were located in the right colon. These 87 adenomas were mostly (79%) under 5 mm in diameter, sessile (89%) and histologically tubular with slight dysplasia (95%). Only 3 adenomas over 10 mm in diameter and tubulovillous presented severe dysplasia. This high incidence of right colonic adenomas differs significantly from findings in other endoscopic series but is in line with the findings of an autoptic study of colorectal polyps (21% of the adenomas were found in the right colon). In addition both in the autoptic study and the present endoscopic series the adenomas of the right colon were small, only slightly dysplastic, unlikely to evolve into malignancy and could have been created by the E1 factor hypothesised by Hill et al. These data confirm the low incidence of right colonic cancer and suggest that patients subjected to the removal of small adenomas of the right colon do not require close surveillance.