Light micrograph of colon with tubulovillous adenoma, a tumor arising from the epithelial tissue lining an organ. Unlike more common polyps, which are attached on a stalk, this type (tubulovillous) forms a small upright tube. If the polyp causes discomfort, for instance by obstructing the flow of food along the intestine, it is removed surgically. Some types of polyp may turn cancerous, and are removed as soon as they are discovered.