What causes bowel (colon) cancer?
The cause of bowel cancer, as with other cancers, is due to damage to cellular DNA. This damage results in uncontrolled growth of abnormal cells, which leads to formation of a tumour. In bowel cancer, the tumour commonly starts as a benign lesion (i.e., it does not invade beyond its normal boundary). This benign tumour is commonly referred to as a polyp, which can be seen at the time of a colonoscopy (an exploratory procedure that involves a doctor inserting a thin lit tube into the anus to view the colon) as a pink growth that protrudes into the inside of the bowel. This can continue to grow and invade deeper tissues, at which point it becomes a malignant tumour (cancer) where it can also spread throughout the body via the bloodstream or lymphatic system.