Colon cancer. Endoscope view of a wire mesh stent in the colon of a patient with colon cancer. This adenocarcinoma tumour is obstructing the colon, part of the large intestine. The stent has been placed in the colon and opened up, allowing the passage of digested food. Colon cancer is thought to be linked to a high-fat, low-fibre diet. It can sometimes be treated by excision of the affected area, but if it has spread it is invariably fatal.