Ch14aP6aT7-L3 Sebaceous Ostium &
Catagen Patterns

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F1Ch14a (Q4897): A portion of a sebaceous gland and the respective duct is represented. Sebaceous cells along the luminal surface disintegrate and, in the process, lipids are released. The sebum collects among keratinized lamellae; as the keratinized lamellae separate from their neighbors, they, and the associated lipid deposits find their way along the follicular lumen to the surface.


F2Ch14a: Degenerating sebaceous cells are collected among keratinizing epithelial bridges; the degenerating sebaceous cells show increased cytoplasmic acidophilia and pyknosis. Near the top of the field on the left, a sebaceous duct is cut in cross-section. In areas in which the degeneration of sebaceous cells is complete, the keratinizing epithelial bridges outline empty spaces. To the right, a portion of a sebaceous duct, near its ostium, is represented; a portion of a vellus hair (blue arrow) is present in the lumen.


F3Ch14a: A catagen follicle is cut in longitudinal section. A hyperplastic sebaceous gland lobule is present on each side of the follicle. The hair in the lumen of the follicle is clubbed. Two blue arrows, near the middle of the follicle, define a boundary. A thin layer of nondescript squamous epithelium is present above the defined boundary. Below the arrows, the squamous epithelium has some distinguishing characteristics. The basal layer is prominent; the palisaded cells are columnar (this is a feature of the outer root sheath, but the epithelium lacks the other distinguishing characteristics of such a layer). Below the boundary, the luminal surface is defined by a layer of brightly acidophilic, keratinized debris; in addition, the keratinized debris focally has collected in heaps to produce the pattern of a corrugated surface. Blue arrows, near the extremity of the follicle, define a rounded collection of keratinocytes - some of these cells show individual cell dyskeratosis and, at the neighboring luminal surface, these cells contribute to the zone of brightly acidophilic keratinized debris. This distinctive form of keratinization has a role in promoting the detachment of the hair shaft and its transportation to the surface. A poorly developed bulb is present at the extremity of the follicle.


F4Ch14a: A portion of a regressing bulb is represented. It retains its cup-shape; its partially recognizable basal layer shows regressive changes with dyskeratotic cells, and melanin deposits (physiologic apoptosis as a manifestation of catagen changes). Green arrows identify a zone of laminated fibrous tissue; each lamella is hyalinized. Centrally, the lamellae are concentrically laminated; they form an oblong whorl; this whorl apparently represents an involuted papilla. Beyond the identified area, there is a zone of condensed fibrous tissue in the pattern of a membrane; it apparently represents the fibrous membrane that normally outlines the deep extremity of a papilla, but is hyperplastic.

In chapter 36, the features of a steatocystoma are discussed. The histologic features of a giant pore are presented in chapter 37. In chapter 38 & 39, the basic features of a proliferating pilar tumor are discussed.


Ch14aP6aT7-L3 Nevus Sebaceus

F5Ch14a: Lumens are cut in cross section in the upper portion of the field. In addition to follicular and sebaceous gland components, a dilated sweat duct, cut twice in cross section, is represented. Sebaceous gland lobules are small and poorly developed. A dysplastic hair bulb shows a prominent basal layer; the basal cells have thin, elongated nuclei; focally the basal cells show pseudostratification of nuclei. The section is to one side of the central longitudinal axis. A portion of a cellular papilla is represented. Red arrows identify the margins of a wedge-shaped portion; this wedge-shaped cluster of cells is interpreted as the primitive hair shaft and the enveloping inner root sheath; morphologic divisions are not well defined. An outer root sheath is not defined.


F6Ch14a: In comparing one side of the primitive bulb with the other side, there is some evidence of asymmetry; this asymmetry may be evidence of an expression of the dysplasia.


F7Ch14a: The basic features of the follicular component of an immature nevus sebaceus of Jadasshon are represented. Sebaceous gland components are poorly developed; they are increased in number. Dilated follicular components (portions of the constant component of a follicle) are cut in cross section. One of the rounded defects is empty and is not lined by a condensation of keratinized debris; it is outlined by compressed sebaceous glands. Defects of this type, in the sebaceous lobules of nevus sebaceus, are common; they are not diagnostic. The inconstant component has the features of a primitive, but asymmetrical, hair bulb; the wedge is represented. The streams of cells that outline the wedge are interpreted as precursor of the inner root sheath (continued in CH14aa).


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