The colonic polyps that could be precursors to carcinoma include conventional adenomas and sessile serrated polyps. Conventional adenomas have a microscopically smooth surface with regular round to elongated crypts. Sessile serrated polyps have a microscopically saw-tooth surface and irregular crypts. The possibility of carcinoma increases with size.

This conventional adenomatous polyp has a hemorrhagic surface (which is why they may first be detected with stool occult blood screening) and a long narrow stalk. The size of this polyp--above 2 cm--makes the possibility of malignancy more likely, but this polyp proved to be benign.