F5Ch23: The column of keratotic debris shows parakeratosis. The adjacent epithelium at the base of the column shows evidence of dyskeratosis. Away from the column, the epithelium is cytologically monotonous; the cells have pale, or clear cytoplasm; each cell has a rounded nucleus with delicate chromatin patterns.
This pattern of apoptotic, terminal differentiation (individual cell necrosis) and parakeratosis is seen in limited anatomic sites in certain stages as normal follicles display their cyclic phenomena (see F4Ch10, F3Ch11, F3Ch12, & F5Ch13). These patterns are evidence of an altered type of terminal differentiation that, in normal follicles, is encountered at the junction of the inconstant follicular component with the isthmus of the constant component. In a normal follicle, the disruptive nature of the phenomena might be evidence of a process that eventuates in the desquamation of the keratinized debris contributed by a tripled layered column (i.e., the inner root sheath), and the hair. How remarkably like porokeratosis is this area.