S9C17P9-1: Classically, the grade of fibrosis in the upper portion of the dermis in a lesion of lichen sclerosis et atrophicus (LS&A) is different from the grade of fibrosis in the same region in examples of superficial morphea (or morphea with a superficial component). In this example of LS&A, the epidermis shows laminated and compact hyperkeratosis. The epidermis mostly is an hypertrophied superficial unit and a basal layer (a definable basal unit is not a significant feature). There are spotty, mild vacuolar changes at the dermal-epidermal interface with focal, small, lytic defects. Rete patterns are effaced. There is a zone of edema and telangiectasia in the upper portion of the dermis (the papillary dermis is chiefly affected, but the process probably also involves a portion of neighboring reticular dermis). A lymphohistiocytic collagenosis affects the dermis at the interface between the portion of edematous dermis and the underlying reticular dermis (in this example, the underlying reticular dermis is atrophic; collagen bundles of the underlying reticular dermis are thin and widely spaced in a clear matrix). In areas, the lymphohistiocytic collagenosis is manifested in band-like infiltrates. Some of the vessels in the infiltrates have thickened, hyalinized walls ( LS&A).

S9C17P9-2: At a higher magnification, the lichenoid reaction is focally prominent (blue arrows); it is cell-poor and is associated with a thin, lytic defect containing a few colloid bodies (necrotic keratinocytes). In the area of the blue arrows, the basal layer is interrupted; the overlying epidermis shows the pattern of an hypertrophied superficial unit with no basal unit (a common combination in the setting of lichenoid reactions, especially in an established [ lichen planus-like] phase). The edematous zone beneath the epidermis is irregularly hyalinized, especially near the dermal-epidermal interface. Vessels are ectatic. The lymphohistiocytic collagenosis is represented at the deep interface of the edematous zone. It is concentrated at the interface between the altered fibrous tissue and the underlying, more normal reticular dermis. As in superficial morphea, the altered connective tissue functions as barrier, restricting the migration upward of inflammatory cells into the zone of edematous fibrous tissue and, in turn, denying the infiltrates access to the basement membrane zone.

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