Study of Human Rectal Epithelial Cells In Vitro. II. H³-Thymidine Incorporation Into Polyps and Adjacent Mucosa2

The incorporation of H3-thymidine (H3TdR) into epithelial cells of colonic mucosal excrescences and mucosa adjacent to the excrescences was studied in vitro. The findings were compared with the incorporation pattern of H3T dR in normal rectal tissue. In all excrescences examined, epithelial cells located in the upper third and surface of the crypts incorporated H3TdR. In mucosa adjacent to excrescences containing evidence of hyperplasia, the same abnormality was always found. In mucosa adjacent to excrescences when no microscopic evidence of pathologic abnormality was present, this alteration was sometimes seen. These areas may, on occasion, be Foci of future polyp activity prior to the macroscopic appearance of newly formed excrescences. The data presented support the concept that papillomas and adenomas are derived from surface epithelium.