Ch17P9-L3 Catagen-like &
Follicular Matrical Tumor

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F1Ch17 (R4564): This is a variation in pattern of the same lesion as represented in Ch16. The surface configuration remains the same; the lesion appears to sit upon the skin. To the right and to a lesser degree to the left, the squamous cell patterns, as seen in the pictorials of Ch16, are preserved. To the right, the squamous cell patterns are sufficiently preserved to qualify as “seborrheic keratosis-like,” or as “inverted follicular keratosis-like.” Centrally, irregular columns of basal cells are loosely spaced in a fibrous matrix. The matrix is condensed (more brightly acidophilic) about some of the nests of basal cells. Some of the larger columns show central cavities. Some of the nests are irregularly pigmented, and pigmented debris has collected in some of the cavities. The lesion has seized the fibrous stroma; the interface between the stroma and the underlying dermis is sharply defined. There is no area in which a column of basal cells is in continuity with the epidermis or the squamous cell component of the tumor.


F2Ch17: This is another section showing basically the same patterns. The follicle-like qualities of the squamous cell component on the right are a prominent feature. Again, there is no continuity between the basal cell and the squamous cell components.


F3Ch17: Patterns of an “irritated seborrheic keratosis” are represented in the squamous cell component on the right. A tendency for stroma to condense about the nests of basal cells is suggestive of the relationship between a hair follicle and its fibrous sheath.


F4Ch17: To the right, the well-defined follicle-like components might be best compared to patterns seen in an inverted follicular keratosis. There is a tendency for the columns of basal cells to be vertical in orientation, a follicle-like quality.


F5Ch17: In the squamous cell component, to the left and extending along the top of the field to the right, patterns of an irritated seborrheic keratosis are represented. To the right of the center of the field, two red arrows point to a whorl of squamous cells (squamous eddy). Two blue arrows point to a neighboring population of basaloid cells that resembles, but for a moderate degreee of cytologic atypis, an expanded basal unit of the epidermis. The keratin-filled cysts have infundibular features. A rounded nest of basal cells is isolated in a mildly inflamed, expanded fibrous matrix.


F6Ch17: The patterns of an irritated seborrheic keratosis are represented on the right in the squamous cell component. There are numerous squamous eddies. Most “squamous eddies” might be characterized as incipent follicular lumens of infundibular type. The nests of basal cells are not in continuity with the squamous cell component.


F7Ch17: Fibrous sheaths outline the nest of basophilic cells. Pigmentation is irregular in some of the larger nests. Deposits of hyalin are present in the large nest of basophilic cells in the center of the field.

An interpretation that one component is independent of the other, and that the lesion is representative of a collision of two independent tumors seems to be the least acceptable option. It seems more likely that a cytolytic process in a portion of the tumor - a portion that is committed to catagen-like phenomena - has resulted in a loss of continuity between the matrical, and the squamous cell components.


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