S4C13P5-3: In this field, the basal layer has been destroyed by the cytopathic process; the damaged epidermis has separated from the dermis to form a sub-epidermal vesicle. As is often the case along the floor of subepidermal vesicles, the reaction in the dermis is cell-poor. Inflammatory cells and necrotic keratinocytes are present in the defect. There is a suggestion of a beginning formation of whorls of regenerating keratinocytes at the margins of clustered, necrotic keratinocytes (blue arrows). In addition, some of the cells at the periphery of the clustered, necrotic keratinocytes show rounded outlines and pale cytoplasm (ballooning degeneration). Individual, necrotic keratinocytes are present in the hyperplastic superficial unit among viable, but hypertrophied and pale, keratinocytes (erythema multiforme).

S4C13P5-4: This example of erythema multiforme-like reaction shows marked papillary edema. Focally, the edema has progressed to the stage of early subepidermal (dermatolytic) vesiculation. Focal cytolytic patterns are represented at the dermal-epidermal interface. These changes qualifies the lesion as the so-called dermal variant of EM. This change may be nothing more than a reflection of the zonal variations within individual lesions of EM; it may be related to the site within a lesion that is selected for biopsy.

S4C13P5-5: The lichenoid patterns of erythema multiforme-like processes also affect the adnexa, as manifested in the superficial portion of this sweat duct.

S4C13P5-6: This is an erythema multiforme-like pattern with whorled transepidermal elimination. The lichenoid patterns at the dermal-epidermal interface are focal in distribution. Clusters of necrotic keratinocytes have been discharged into the keratin layer. The pattern is not diagnostic of a single disorder; drug eruption should be mentioned in the differential diagnosis. In view of the focal nature of the mild infiltrates, subacute lupus erythematosus should be considered in the differential diagnosis.