S3C20P8LP


S3C20P8-1: This cell-poor lichenoid reaction in the setting of dermatomyositis is not so clearly erosive at the dermal-epidermal interface as would be a cell-rich lichen planus-like reaction.the cell-poor reaction is characterized by effacement of the rete ridges and by liquefactive changes at the dermal-epidermal interface. In contrast, in lichen planus-like reactions, the rete ridges are often preserved but distorted; lytic defects are often prominent along the margins of the rete ridges. The partially preserved rete ridges of a lichen planus-like reaction often have pointed extremities (i.e., “saw-toothing”). In this example of a cell-poor lichenoid reaction in the setting of dermatomyositis (and, when represented, is characteristic of the reaction in dermatomyositis), the rete patterns are effaced. Basement membrane changes are not as prominent a feature of lesions of dermatomyositis as they are in lesions of lupus erythematosus. With the exception of a single row of altered basal cells, the epidermis is composed of cells showing the markers of terminal differentiation (i.e., cells of the superficial unit of the epidermis). Above the basal layer, the cells have their long axes parallel to the basement membrane. The basal layer is chiefly affected by the lichenoid process. The widened, edematous papillary dermis contains a few pale colloid bodies (i.e., necrotic keratinocytes). Melanophages, in the dermis, are a marker for damage to the basal layer. A dermal vessel is ectatic.


S3C20P8-2: In this lesion, established lichen planus-like reactions affect the epidermis and a hair follicle. A cytolytic T lymphocyte reaction has produced lysis of the basal unit of the two epithelial anatomic components of the skin. The epidermis is hyperplastic; rete ridges are arranged in complex patterns. Many of the rete ridges are elongated and thin; they have pointed extremities. The cleft, in the dermis on the right, is an artefact. The lesion is cell rich in the adventitial dermis (i.e., the papillary dermis and the perifollicular connective tissue sheath); the infiltrates fill the adventitia and hug the epithelium. The altered kinetics associated with a hyperplastic superficial unit have eventuated in the formation of the compact, keratinized product in the lumen of the follicle. This combination of features satisfies the requisites for the diagnosis of lichen plano-pilaris, but it should be noted that these features are expressive of a common pathway, accessible in a variety of clinical settings.

S3C20P8-3: In a late stage, the follicular changes of a lesion of lichen plano-pilaris are characterized by a reduction in the density of the cellular infiltrates and by atrophy of follicular epithelium. The follicle ceases to cycle. The extremity of the affected follicle is eroded. The affected cells are those of matrical type; they are required for the formation of a hair bulb and for the induction of a papilla. The follicle may persist for a time as an ectatic epithelial lined sac. Erosion of the epithelium in the region of the infundibulum and perifollicular fibrosis combine to produce complete atrophy of the follicle. A vertically oriented connective tissue domain would then persists as a marker for the site in which the epithelium of a follicle has atrophied.

S3C20P8-4: The erosion of the basal layer of the epidermis in a lichen planus-like reaction may disrupt cohesion between epithelium and dermis; a subepidermal bulla is the result. Lichen planus-like changes beneath the blue arrows to the right reveal the nature of sub-epidermal vesicle to the left ( bullous lichen planus).

S3C20P8-5: Bullous on the left and lichen planus-like on the right.

S3C20P8-6: At the margin of the defect seen in P8-5, the classic defect of non-bullous lichen planus-like reactions is represented. The cleft occupies the former domain of the basal unit of the epidermis. It contains necrotic keratinocytes, lymphocytes, histiocytes, and melanophages. Cells, of what can be characterized as an altered superficial unit of the epidermis, are hypertrophied and pale. They have plump nuclei and nucleoli, and prominent inter-cellular bridges.

S3C20P8-7: In this bulla, the cellular exudate in the defect is remarkably similar to the contents of the cleft in figure S3C20P8-6. This cellular component serves as a marker for the lichen planus-like character of the process, even in the bullous component. The blue arrows point to a collection of colloid bodies.

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