Ch26P18-L3 Catagen-like &  
Sebaceous Tricholemmoma

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F1Ch26 (R2353): Prominent whorls (squamous eddies), and a dual population of keratinocytes are represented. The larger keratinocytes are constituents of the whorls and might be characterized as having features similar to those of the cells of an epidermal superficial unit (i.e., cells that with maturation will enter the process of terminal differentiation). In this field, the small (germinative) cells (the second component of the dual population) shows unusual nuclear features (see F2Ch25). Small sebaceous gland lobules are irregular in distribution. In the left upper corner, many of the squamous cells show perinuclear vacuoles; this quality might be interpreted as evidence of tricholemmal differentiation. On the other hand, the cells are basically common squamous cells; they have more abundant cytoplasm than the neighboring small cell population. This type of vacuolar change is basically a feature of the large cell population; it is peculiarly related to areas of cytolysis and dyskeratosis. I believe that the vacuolar change is evidence that the epithelial cells have committed to the cytopathic changes of catagen phenomena.


F2Ch26: One of the small sebaceous gland lobules is represented. The cells of the small-cell population have plump, round nuclei with diffuse, delicate chromatin patterns; they have a prominent central nucleolus. These cytologic features might be cited as evidence that the cells are germinative cells of sebaceous type.


F3Ch26: At a slightly more superficial level, the termination of the sebaceous gland lobule is represented; the lumen that extends beyond the sebaceous gland lobule is the lumen of the sebaceous gland duct. The thin border of condensed, acidophilic keratinized debris is a characteristic of a sebaceous gland duct.


F4Ch26: In this field, the population of germinative cells and the whorls of keratinocytes, showing ductal differentiation of sebaceous type, are represented. To the left of the left row of arrows, a population of plump, pale keratinocytes is represented; some of the cells show vacuolization of the cytoplasm; scattered cells show evidence of dyskeratosis. The changes in the latter area are representative of a cytolytic process having apoptotic properties. These areas of lysis perhaps express an economy in which cells that have failed to form sebaceous cells can be removed from the community.


F5Ch26: Sebaceous ductal changes are prominent in the central portion of the field. To the right at the bottom of the field, cytolytic and dyskeratotic changes are a prominent feature.


F6Ch26: Focally, some of the cells bordering the lumens of the sebaceous ducts contain keratohyalin granules. The patterns are such that this portion of the lesion has sebaceous duct qualities.

The patterns overall are compound and follicular; they include those of an infundibulum-like type, a sebaceous gland-like type, and inconstant epithelial type with catagen-like attributes.

In chapters 40a & 40b, the histologic features of sebaceous adenomas are discussed.



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