Colon polyp. Coloured 3D computed tomography (CT) colonoscopy image of a pedunculated (stalked) polyp in the sigmoid colon (large intestine) of a 50-year-old patient. Polyps are benign (non-cancerous) growths that arise from mucous membranes. Although benign, polyps are generally removed surgically as their growth may obstruct the passage of food, and some polyps may turn cancerous over time. This polyp measures approximately 10mm across.