HYPERPLASIA AND FLUID ACCUMULATION IN EPITHELIAL CYST FORMATION AND GROWTH

Epithelial cysts may develop in virtually any epithelium. All cysts, r egardless of their origins, are characterized by epithelial hyperplasi a and fluid accumulation. Additional features may include tubular atro phy, basement membrane alterations and association with inflammatory c ells. In spite of the intense research effort in recent years directed at uncovering the cellular mechanisms of cyst development and growth, we still do not know the primary events that lead to cyst formation. However, there are at least three candidate mechanisms. These include: 1) increased cell proliferation (epithelial hyperplasia) in the cyst wall, 2) net fluid accumulation in the cyst cavity and 3) alterations of extracellular matrix components linked to cyst formation and growth . This review discusses the evidence to support the role of each mecha nism as a possible primary event necessary for cyst initiation and con tinued enlargement. Present data on the pathogenesis of epithelial cys t formation strongly suggests that no single mechanism, as yet describ ed, can adequately account for all situations of cyst occurrence.