Dysplasia in the gastrointestinal tract: definition and clinical significance.

The term "dysplasia" is used increasingly in gastrointestinal pathology. Dysplasia denotes an unequivocal neoplastic epithelial alteration without invasive growth and is synonymous with the term "intraepithelial neoplasia." Dysplasia is the paradigm of a precancerous lesion. Confusion arises because some pathologists do not use the term in the above-defined sense but to describe regenerative, inflammatory and reactive changes. It is essential to separate these kinds of non-neoplastic epithelial changes from neoplastic dysplasia because the clinical consequences are completely different. The general morphology and the grading of dysplasia are described. Most dysplasias in the gastrointestinal tract are the polypoid lesion; dysplasias in flat mucosa are uncommon. Knowledge of the incidence of dysplasia in the gastrointestinal tract is important for the concept of secondary cancer prevention.