According to WHO statistics, in 1996 875,000 new cases of colorectal cancer were diagnosed and 495,000 deaths were attributed to it worldwide 1. It is the third most common cause of cancer deaths and its incidence and mortality rates continue to rise.
Most colorectal cancers develop via a characteristic series of pathological steps (Fig. 1). Colorectal epithelial cells acquire abnormal growth and morphological characteristics and form an adenoma, a tumor mass often protruding into the lumen of the colon or rectum. In time, these lesions enlarge and a subset of cells can acquire additional abnormal growth behaviors, which allows them to invade into the bowel wall and metastasize. At this point, the tumors are classified as adenocarcinomas and can be lethal. In the course of this typical multistep process, somatic mutations develop in key genes in...
