Ch13aP5a-L3 Catagen Patterns
(ghost cells)

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FigJ4230trichlem310 FigJ4230trichlem320

Fig1Ch13a (tier 4) (the first 3 photos of this chapter are representative of material from a different patient than those of the preceding chapters along this tier) (J4230): This follicle was a neighbor to a tricholemmoma. It is a miniturized follicle showing catagen patterns. The plane of the section is somewhat eccentric. In the picture on the right, the infundibulum and outer root sheath are represented. The extremity of the follicle has reverted to a resting state (a population of small squamous cells with a prominent row of palisaded basal cells. Cells of this deep component form arms that embrace a cluster of plump vacuolated cells. Cells in a cluster, having undergone the transformations that occur in the catagen stage, have taken on a vacuolated quality, and have lost the distinctive phenotypic markings of an anagen phase. These cells, in turn, appear to have contributed the dense collection of ghost cells that defines a pattern of the catagen stage. The thin arms of non-vacuolated cells might present a sharp interface with the cluster of vacuolated cells. A lack of distinguishing cytologic features precludes an identification of either population of cells with a component of an anagen follicle. If we go to the more recognizable zone of what might be an altered outer root sheath (at a more superficial level), the keratinized product is a layer of more uniformly flattened, keratinized lamellae. The cells that have contributed the ghost cells might tentatively be identified as catagen-influenced cells of the trichogenic portion of the hair bulb. With one more step in the conceptualization of the changes, a pilar cyst then becomes a catagen-influenced, hair matrical cyst.

FigJ4230trichlemCA330

F2Ch13a (tier 4) (J4230): Partially involuted epithelium of the outer root sheath (recognizable by the vacuolated cells among non-descript squamous cells near the top of the field) have produced a uniform layer of pink keratinized debris. This layer of keratin ends at about the level of the constriction just above the center of the field. Below the constriction, polygonal (variation of ghost cell) brightly acidophilic keratinized debris is present in the lumen. There are scattered vacuolated cells on both sides of the acidophilic debris. The bright red debris (ghost cell-like) has a role in the upward movement and detachment of a hair shaft during the catagen phase. Near the bottom of the field, there is a rounded cluster of plump, vacuolated cells. Cytologically, they somewhat resemble the distinctive cells of the outer root sheath of an anagen follicle but are situated in a site more characteristic of the matrix of the hair bulb of an anagen follicle. It is, perhaps, asking too much to look at the epithelium of a catagen phase follicle and, then, attempt to pick out populations that are correspondents of those of an anagen hair bulb; each phase has its own distinctive phenotypes. In any case, the vacuolated cells of the cluster make a contribution to the ghost cells in the lumen; they contribute to the cellular kinetics that are responsible for the movement of a detached (clubbed) hair upward and out of the catagen follicle. The cluster of vacuolated cells might be characterized as the bulge as expressed in catagen patterns.

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F3Ch13a: This catagen follicle shows a bulge above the center of the field. Some of the cells of the bulge have vacuolated cytoplasm; The cellular bulge is outlined by a glassy membrane; this association, might be taken as evidence that the bulge consists of altered cells of the outer root sheath. It is, however, more appropriate to not attempt to compare populations of cells in a catagen follicle with the components of an anagen follicle. Cells of the central portion of the bulge show dyskeratosis. Below the center of the field, the thin column of squamous cells has two distinguishing features, a palisaded basal layer and a cup-shaped extremity with melanin deposits; about this portion, the fibrous sheath is wide and laminated. The remnant of the bulb is represented at this level; it apparently has just relinquished its papilla.

inflamdisy4

F4Ch13a: This drawing has been borrowed from the material on inflammatory diseases. It was designed to define functioning units of the epidermis (but generally is applicable to squamous epithelium), and to characterize the component cells. These concepts of functioning epithelial units in squamous epithelium have application in the interpretation of patterns in neoplasms of squamous epithelium (including follicular disorders). Cells of the basal unit tend to be cuboidal or rectangular with a long axis that is vertically oriented in relationship to the adjacent basement membrane. Cells of the basal unit tend to show cytoplasmic basophilia in comparison to the cytoplasmic acidophilia of the cells of the superficial unit. A mucinous interstitium of the basal unit facilitates the exchange of nutrients and waste between epithelium and stroma. The basal unit is more of an immunologically active domain than is the superficial unit; Langerhans mostly reside in the basal unit. Cells of the superficial unit are acidophilic, an attribute contributed by the process of keratinization. They are larger than basal cells and tend to be elongated with a long axis that is parallel to the adjacent basement membrane. In contrast to the interstitium of the basal unit, the interstitial avenues of the superficial unit is closed by a lipid-rich membrane. The formation of the membrane is facilitated by the release of Odland bodies (keratinosomes) into the interstitium. Physiologic apoptosis provides for a uniform population of cells; the process includes lysis of cells and individual cell dyskeratosis.

inflamdisy14

F5Ch13a: This drawing had application to patterns seen in psoriasiform processes. In a lesion of psoriasis, basal unit hyperplasia is manifested in a relatively pure form. The basal unit is hyperplastic to a degree that the changes affect normal keratinization in the superficial unit; the product at the surface is parakeratotic, and the resulting superficial layer of keratinized debris is a poor barrier, both immunologically and environmentally. The lipid membrane of the superficial unit in a psoriasiform process is poorly developed. This compromise of events in the altered superficial unit facilitates a persistence of a mucinous interstitium. Inflammatory cells, particularly neutrophils, easily find their way through the open mucinous avenues to collect in the parakeratotic cap; the resulting pattern is spoken of as a Munro abscess or, depending on the severity of the migration, as a spongioform pustule.

inflamdisy5

F6Ch13a: With this drawing, an attempt was made to depict the phases of a lichenoid reaction. The primary stage essentially is a florid psoriasiform pattern. The established phase more or less corresponds to what might be characterized as a classic lichenoid reaction. In this stage, the immune reaction results in lysis of the basal layer and a portion of the basal unit. Lytic defects, containing dyskeratotic cells, are the prime characteristic of such an established phase. As a defensive response, the superficial unit undergoes hypertrophy; individual cells of the superficial unit are enlarged and acidophilic; in the act, mucinous avenues are closed and migrating inflammatory cells tend to be denied access to this altered superficial unit. In neoplasia, the influence of inflammatory cells is variable. In addition, lysis and dyskeratosis may be a programmed expression of the neoplasm. These attributes usually are expressed in cells of basal unit type. In tricholemmal follicular neoplasms, cells such as those of the inconstant portion of a follicle, and as seen in catagen phases of follicular cycles, similar programs resulting in similar mophologic defects are expressed).

In chapter Ch35P27, the distinguishing features of a pilar cyst are discussed. The patterns, at the interface between viable cells and keratinized debris, can be compared to those seen in a catagen follicle in the region about the club of a clubbed hair.

 

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