Wednesday 20 June 2007
Dysplasia is encountered principally in epithelia, and it is characterized by a constellation of changes that include a loss in the uniformity of the individual cells as well as a loss in their architectural orientation.
Dysplastic cells also exhibit considerable pleomorphism and often contain hyperchromatic nuclei that are abnormally large for the size of the cell. Mitotic figures are more abundant than usual, although almost invariably they conform to normal patterns.
Frequently the mitoses appear in abnormal locations within the epithelium. Thus, in dysplastic stratified squamous epithelium, mitoses are not confined to the basal layers and may appear at all levels and even in surface cells. The architecture of the tissue may be disorderly.
For example, the usual progressive maturation of tall cells in the basal layer to flattened squames on the surface may be lost and replaced by a scrambling of dark basal-appearing cells throughout the epithelium.
When dysplastic changes are marked and involve the entire thickness of the epithelium, but the lesion remains confined to the normal tissue, it is considered a preinvasive neoplasm and is referred to as carcinoma in situ .
Once the tumor cells move beyond the normal confines, the tumor is said to be invasive. Dysplastic changes are often found adjacent to foci of invasive carcinoma, and in some situations, such as in long-term cigarette smokers and Barrett esophagus, severe epithelial dysplasia frequently antedates the appearance of cancer.
However, dysplasia does not necessarily progress to cancer. Mild to moderate changes that do not involve the entire thickness of epithelium may be reversible, and with removal of the inciting causes, the epithelium may revert to normal.
biliary epithelial dysplasia
Vulvar epithelial dysplasia (by Washington Deceit)