Significance of precancerous lesions in the colon and rectum.

The turnover of the colonic mucosa sheds some light on the understanding of the precancerous stages. The colon mucosa operates through a constant and regular epithelial renewal. The regularity of this cycle is controlled by two membranous systems: the basement membrane as a sliding support- coat and the as a brake in the cells progression and thus in the mitosis. Any disturbance, in these system, brings about a large extension of the proliferative area, according to modalities common to all varieties of precancerous, polypous or non-polypous condition. On this poll of undifferentiated cells, with frequent mitosis risks of cancerous changes are, all the higher, that the undifferentiated areas or growing areas are more extended. This explains the unequal tendency to malignancy of colitis, solitary polyps, villous polyps in layers, and multiple polyps.