S4C13aP5a-EM



S4C13aP5a-1: An area showing the pattern of whorled transepidermal elimination is outlined by green arrows. Several clusters of necrotic keratinocytes are arranged back to back. The clusters, in turn, are outlined by several layers of concentrically arranged, hypertrophied keratinocytes.In toto, the various components form one large whorl. The classic lichenoid pattern of erythema multiforme affects the basal unit of the epidermis beneath the whorl. As a property of epidermal kinetics, keratinocytes move upward to the surface; in this process, a whorl, as represented in this field, will be carried upward and discharged into the keratin layer. This upward movement is, in part, dependent on continued active replication of cells in a basal unit.

S4C13aP5a-2: In this field, the lichenoid patterns of EM are represented. To the right, the process has progressed to the formation of a subepidermal defect; the defect contains necrotic keratinocytes, lymphocytes, and histocytes (blue arrows). In this localized area, the reaction has the characteristics of an established lichenoid reaction (lichen planus-like). Several, characteristic whorls are present in the superficial unit of the epidermis; yellow arrows outline a small, young whorl. Beneath the green arrows, a small area shows partial preservation of a basal unit. The lymphoid infiltrates are mostly confined to the domain of the basal unit of the epidermis. Confinement in this manner is not peculiar to the erythema multiforme-like variant of a lichenoid reaction.

S4C13aP5a-3: This is a vesicular lesion in the setting of lupus erythematosus. A cleft has formed at the dermal-epidermal interface in the region beneath the green arrows. The lesion is an early subepidermal vesicle. There are perivascular infiltrates of lymphoid cells; they extend into the papillary dermis to the dermal-epidermal interface. The patterns are lichenoid.

S4C13aP5a-4: The basal unit of the epidermis in the region of the subepidermal defect shows extensive degenerative changes. This extensive necrosis of the basal unit of the epidermis has resulted in detachment of the epidermis from the dermis. The patterns in the basal unit have an erythema multiforme-like quality.

S4C13aP5a-5: At this margin of the vesicle, the lichenoid changes are of a type seen in erythema multiforme-like processes. There is necrosis of the basal layer with focal loss of a defined basal unit. The viable epithelium mostly has the qualities of a hyperplastic superficial unit. In contrast to many lesions showing an EM-like pattern, there is compact hyperkeratosis. In areas to the right, the damage to the epidermis has produced a zone of parakeratotic debris along the skin surface. Melanophages are present in the dermal infiltrates. Centrally, clusters of necrotic keratinocytes are on their way to the surface ( whorled transepidermal elimination). A pityriasic variant of a lichenoid reaction must also be considered in the differential diagnosis.

S4C13aP5a-6: Centrally, the pattern of whorled transepidermal elimination is represented. On the other hand, the well-developed lytic defects containing lymphocytes, histiocytes, and clusters of necrotic keratinocyte are reminiscent of changes seen in lichen planus-like variants of the lichenoid reaction. The latter patterns may be seen in more severe examples of EM-like reactions. Perhaps, this is EM complicating LE. Perhaps, it an EM-like expression of subacute LE in bullous patterns.

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