Endocervical mucosal surface epithelium that everts out onto the portio may become replaced by squamous epithelium in two ways: (1) by overgrowth from adjacent regenerative ectocervical epithelium, as in ascending repair (Figs. 10-13), or (2) by squamous metaplasia of the reserve cells of the endocervical epithelium, as in descending repair. Both processes may occur simultaneously or separately. In general, ascending repair is stimulated by endogenous or exogenous estrogens, whereas descending repair predominates under endogenous or exogenous gestagenic stimulation (Dallenbach-Hellweg 1981). Descending repair is preceded by a double- or multilayered hyperplasia of the reserve cells (Figs. 19,2o),which,in accordance with their cytokeratin endowment, undergo metaplastic change and differentiate into squamous epithelium (Figs. 21,22). Some of these metaplastic cells, however, may retain their bipotential capacity and produce mucin, thereby being responsible for the monocellular mucin formation occasionally seen in squamous cell metaplasia of the endocervix (Figs. 23,24).
During maturation to squamous cells, their capability to produce mucin is usually lost. In contrast, the squamous epithelium adjacent to the endocervical epithelium expresses cytokeratins of the squamous epithelium type in all layers, whereas the columnar epithelium neighboring it exhibits a positive reaction only in the underlying reserve cell layer (Fig. 25). With mucin stains, a faint positive reaction may be detected in the superficial cell layer, which may include the flattened atrophic remnants of columnar cells that originally covered the reserve cells (Figs. 26,27).
Was this article helpful?
Learning About 10 Ways Fight Off Cancer Can Have Amazing Benefits For Your Life The Best Tips On How To Keep This Killer At Bay Discovering that you or a loved one has cancer can be utterly terrifying. All the same, once you comprehend the causes of cancer and learn how to reverse those causes, you or your loved one may have more than a fighting chance of beating out cancer.