Colonic polyp. Endoscope view of a benign (non- cancerous) polyp in a patient's sigmoid colon, the part of the large intestine that joins to the rectum. Polyps often cause no symptoms, although they may obstruct the flow of food through the intestine if they grow large. Some polyps may turns cancerous (malignant), and polyps are generally removed surgically to ensure that this does not occur.