Cell proliferation in gastrointestinal carcinogenesis.

During the course of carcinogenesis in the intestinal tract a series of proliferative changes occur which may represent pre-neoplastic abnormalities. These include progressive crypt hyperplasia, expansion of the proliferation zone within the crypt and alterations in the numbers and distribution of proliferating cells. The literature documenting these changes has been reviewed and their significance as pre-neoplastic phenomena assessed. Major problems include the differentiation of coincidental adaptive changes from truly pre-neoplastic ones, and the integration of morphological and kinetic observations.