The molecular basis of dysplasia.

Detailed descriptions of the molecular pathways involved in dysplasia and carcinoma would fill many bound volumes. This article illustrates the molecular concepts involved in the pathogenesis of dysplasia and carcinoma, with examples that are most relevant to the gastrointestinal tract. At this time, there are at least 4 circuits that must be altered for a cell to become dysplastic: 1) requirement of a continuous or autonomous growth stimulus, 2) development of resistance to growth inhibitory signals, 3) avoidance of apoptosis, and 4) ability to transcend the limits imposed by the generational clock. Although it is likely that 1 or 2 additional circuits must also be altered for the development of carcinoma, they are not defined at this time.