S3C19P7-Lichen Planus

S3C19P7-1: Lichen planus is characterized by a distinctive histologic pattern. The pattern is so characteristic that the clinical presentation is generally accepted as representative of a specific disorder. Clearly, the category is etiologically heterogeneous. For example, some of the patterns, as encountered in the setting of lichen striatus, would be readily accommodated in the category of “lichen planus.”

S3C19P7-2: The classic features of a lesion of lichen planus are represented. There is compact hyperkeratosis with a prominent granular layer. A band-like infiltrate of lymphoid cells fills a widened papillary dermis. The infiltrate hugs the epidermis and has migrated a short distance into it. The basal layer is focally interrupted; a mophologic basal unit is not identifiable in the area of inflammation. A small lytic defect in the epidermis contains coagulated keratinocytes. Melanophages are present in the dermal infiltrates. A partially preserved rete ridge has a pointed extremity. The superficial unit is hyperplastic; its individual cells are hypertrophied. This alteration in the character and expanse of the superficial unit might be characterized as a compensatory hyperplasia and as a defensive process in which the closed interstitial spaces deny the aggressive T lymphocytes access to what otherwise would be target cells.

S3C19P7-3: In this established lichenoid reaction (i.e., lichen planus-like reaction), all the features of figure S3C19P7-2 are represented, but the lytic defects are more prominent at the dermal-epidermal interface. There are scattered necrotic keratinocytes in the defects and, focally, a few are present in the overlying superficial unit.

S3C19P7-4: The clefts (Max-Joseph) are a common feature of lichen planus-like reactions. They are in large part an artefact related to the effects of processing of tissue in which damage to the basal layer has reduced the cohesion between epidermis and papillary dermis.

S3C19P7-5: This lichen planus-like lesion shows sparse lymphoid infiltrates in a widened, fibrotic papillary dermis. Melanophages are prominent. Lytic defects are present at the dermal-epidermal interface. The sparse infiltrates, the cell-poor quality of the reaction at the dermal-epidermal interface, and the widened papillary dermis identify the patterns as those of early senescence in a lichen planus-like reaction.

S3C19P7-6: This annular lesion shows an area of epidermal atrophy to the left. Rete patterns are effaced and lymphoid infiltrates are sparse. The changes to the left are those of a senescent lichenoid reaction. At a clinical level, such changes might appear atrophic. To the right at the periphery of the lesion, the patterns are those of an established lichen planus-like reaction. The combination of features qualifies as atrophic lichen planus.

S3C19P7-7: The central area of atrophy is characteristic of atrophic lichen planus. This pattern qualifies histologically as a senescent lichenoid reaction. The same changes, in the proper clinical setting, would qualify as poikilodermatous. Poikiloderma generally is a senescent lichenoid reaction.

 

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