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1. Histopathology of Inflammation

2. Minimal Deviation Melanoma, etc.

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F1Ch11 (R4564): This small follicle has a well-defined bulb and papilla. The central hair shaft is cellular. Huxley’ and Henle’s layers are well-defined. The non-trichogenic portion of the bulb is in continuity with Huxley’s layer. Above the bulb, a single row of flattened spindle cells define the outer limits of the outer root sheath. Below this defined boundary, a thin fibrous sheath is continuous from one side to the other; it confines the papilla.

F2Ch11: Purple arrows identify the fibrous sheath that confines the bulb (in perineurium-like patterns). Yellow arrows define the interface between the “cuticle” (at this level a single row of dark cells) and the cellular, developing hair shaft. It is difficult to identify the “cuticle” of the inner root sheath but there is an ill-defined row of pale cells (green arrows define the interface abutting upon Huxley’s layer). Plump, round, clear cells, at the outer limits of the bulb, appear to be in continuity with Huxley’s layer.

F3Ch11: In cross-section, these patterns are interpreted as the upper limits of the outer root sheath. The polygonal keratinized cells are the terminal product of the inner root sheath.

F4Ch11: A clubbed hair is not represented but the patterns of keratinization are characteristic of the catagen-like type as seen in a follicle that is engaged in pushing a clubbed follicle to the surface - one in which the phenotypic structural features of anagen phenomena have ceased to influence cytologic features. Perhaps, it is in this field that the significance of the eosinophilic granular cells, in streaming patterns, and as seen in examples of pilomatrixoma, can be characterized as to type; the vertically oriented, brightly acidophilic cells are on their way to keratinization and sequestration. In this eosinophilic column, the files of single cells show perinuclear vacuoles and karyolysis. Deposits of coarse melanin granules are also a marker for degenerative changes. Near the top of the field, the cells of the outer root sheath show scattered areas in which there is an reduction in the number of nucleated cells. The area that bulges is the “catagen bulge,” as seen in the phase of catagen phenomena. The phenomena and the cytologic features make it difficult to identify components in the patterns that would correspond to the varied populations that characterize anagen phenomena and cytologic features.

F5Ch11: This catagen follicle shows changes of the type seen in association with a clubbed hair, but a hair is not represented in the plane of this section. In the bulging portion, just to the right and above the center of the field, both the outer and the inner root sheaths have relinquished their anagen-related phenotypes; they have reverted to relatively non-specific squamous cells. To the left of the follicle, just below the sebaceous gland, thin fascicles of smooth muscle cells are attached to the basal layer of the neighboring follicular epithelium; each attachment produces a distortion of the contour of the basal layer. Each fascicle is separated from its neighboring fascicle by a loosely cellular, clear matrix; perhaps, this is the “hair disk.” A strand of squamous epithelium extends to about the center of the field. It is outlined by a glassy membrane that focally is wavy. It has a basal layer showing prominent palisading of nuclei. At its deep terminal, it abuts upon a nodule of fibrous tissue.

F6Ch11: At the level of the junction of the infundibulum (identified by a luminal row of granular cells containing keratohyaline granules), and the sebaceous ducts (characterized by a lack of keratohyalin-rich cells), there is a contriction that reduces the diameter of the epithelial component. Loosely cellular, loose fibrous tissue appears to compress the follicle in this areas. This type of constricting perifollicular fibrosis generally anticipates atrophy of the inconstant portion of the follicle. The end-result is an inability to again enter an anagen phase; the process produces an isolated scarring alopecia; this type of perifollicular fibrosis has, on occasion, been characterized as being representative of changes seen in one type of pseudopelade. In this case, a pilomatrixoma was present in the adjacent dermis, and apparently had been treated with injections of steroids.