S4C15P7TEN


S4C15P7-1: In this lesion of erythema multiforme, the keratin layer is little affected. This is a characteristic feature of early lesions. In older lesions, the extrusion of cellular debris at the surface will alter the character of the keratin layer. In this lesion, the damage is diffuse at the dermal-epidermal interface. A cytopathic focus in the superficial unit to the right of the center of the field shows lysis of keratinocytes. There is a second cytopathic focus in the adjacent basal unit; it is rounded in outline. In the reticular dermis, infiltrates are perivenular. The combination of features qualifies the reaction as a lichenoid lymphocytic vasculitis. There are collections of extravasated red blood cells.



S4C15P7-2: At higher magnification, a lytic defect in the basal unit contains dead, and dying, keratinocytes (apoptotic changes). This is the type of defect that, in the process of repair, will induce whorled regeneration of neighboring keratinocytes (should this potential be included in the category of apoptotic phenomena?). Orange arrows identify the basement membrane. It appears to be intact; duplications do not appear to be a prominent feature. Green arrows identify degenerating keratinocytes with intra-nuclear inclusions.

S4C15P7-3: Even the lichenoid reaction of erythema multiforme-like type has a life history. In older lesions, as in this example, the process may acquire some of the qualities of an established lichenoid reaction (qualities that are lichen planus-like). In this lesion the superficial unit shows some of the changes that characterize a lichen planus-like reaction. A basal unit is not a feature. On the other hand, the keratin layer is relatively normal.

S4C15P7-4: This pattern is clearly lichenoid. Clinically, the process was thought to represent a drug eruption. At this magnification, the process is lichen planus-like. Compact hyperkeratosis, a prominent granular layer, eroded rete ridges with pointed extremities, and a hyperplastic superficial unit are all features of a lichen planus-like process. With occasional exceptions, these are not features of pityriasic disorders. On the other hand, the infiltrates are sparse in the papillary dermis and are prominent in the perivascular spaces of the reticular dermis. At this magnification, the lesion qualifies as a lichenoid lymphocytic vasculitis of lichen planus-like type.

S4C15P7-5: At a higher magnification, focal areas of parakeratosis interrupt the pattern of compact orthokeratosis. The pattern at the dermal-epidermal interface is cell-poor. This cell-poor quality may be a measure of a stage in the life history of the lesion. This lesion may be late in its evolution; it is regressing. The patterns might be appropriately characterized as a senescent lichenoid reaction.

S4C15P7-6: This is the classic histologic pattern of an erythema multiforme-like process. There are prominent clusters of necrotic keratinocytes. The basal layer of the epidermis shows extensive, diffuse damage. On the basis of clinical presentation, the process was interpreted as toxic epidermal necrolysis. In another clinical setting, the changes would be compatible with a fixed drug eruption.

S4C15P7-7: In this example of toxic epidermal necrolysis (drug related), the epidermis has separated from the dermis. A basal layer is not represented in the roof of the defect. Scattered lymphocytes and necrotic keratinocytes are present along the deep surface of the roof of the defect. They serve as markers for a lichenoid process. There are spotty perivascular infiltrates of lymphoid cells in the dermis. Defects in the epidermis contain loosely clustered, necrotic keratinocytes.

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