Colon cancer & polyp. X-ray of an apple core" tumour at the junction of the rectum (lower right) and colon (centre left). This tumour has grown in a ring around the inside of the intestinal wall, causing severe constriction. The patient also has a pedunculated (stalked) polyp in the colon, an abnormal growth that could become cancerous. This is the dark circle in the bright part of the colon just to the left of the apple core tumour. The light areas inside the intestine on this X-ray are produced by an X-ray-opaque substance given to the patient. The ball-and-socket joint of the patient's left hip is in the lower left."