Origins and morphogenesis of colorectal neoplasms

Gastrointestinal stem cells are considered pivotal in colonic carcinogenesi s. There is evidence to suggest that early microadenomas in the colon are p olyclonal in origin. Adenomas, once initiated, enlarge by the process of cr ypt fission. It is also the main mechanism by which neoplastic clones sprea d through the colorectal epithelium. Both concepts are important for our un derstanding of the early events in colonic carcinogenesis.