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Abstract

During an 8-year period, 747 adenomatous polyps were removed either alone or in association with a known colonic cancer. These adenomas were reviewed to determine whether benign-appearing adenomatous epithelium could be located below the level of the muscularis mucosae unassociated with the additional pathologic signs of invasive cancer. Of 637 polyps unassociated with cancer resection, 3.2% showed evidence of benign “misplacement,” while this entity was found in 28% of the adenomas removed in association with 596 resections for cancer. Adenomatous misplacement is associated with cystic dilatation in the polyp head, hemosiderin deposition in the stalk, and normal lamina propria which surrounds adenomatous tissue appearing below the muscularis mucosa. Cytology of the “misplaced” structures is identical to the benign adenomatous pattern seen on the polyp surface. This entity must be differentiated carefully from the appearance of invasive cancer in adenomatous polyps in order to avoid unnecessary radical colonic resections. Previous statistical analyses regarding the association of gross malignancy and “invasive cancer” in adenomas need to be critically analyzed.