Have significant genetic differences in addition to well known clinical differences

Cancer of the large bowel is the third commonest cancer, and second commonest cause of death due to cancer in the United Kingdom. In 1994, there were 28 904 registered new cases and about 15 740 deaths from colorectal cancer in England and Wales.1 Differences in clinical presentation and surgical management of right and left sided large bowel cancer are well known. For example, right sided tumours typically present at a more advanced stage with symptoms of weight loss and anaemia, whereas left sided tumours often present with rectal bleeding, change in bowel habit, and tenesmus. However, we are now aware of increasing differences in the molecular pathology of carcinomas depending on their laterality within the large bowel. These differences will become more relevant as systemic treatments improve.

The large bowel includes both the colon and the rectum. It is continuous, with no definite point microscopically where colon ends and rectum begins. From an anatomical and surgical point of …