S4C17P9PLVA



S4C17P9-1: This is a representative pattern for a lesion of pityriasis lichenoides et varioliformis acuta (PLVA). The reaction is clearly lichenoid. The superficial unit is hyperplastic, but the lesion is not a classic example of a lichen planus-like process. The superficial unit shows a distinct pallor. There is a perifollicular component, but not in the pattern of an established lichenoid reaction. Rete ridges are partially preserved at the dermal-epidermal interface. The dermal-epidermal interface is obscured by lymphoid infiltrates. There are prominent perivenular components; the process is a lichenoid lymphocytic vasculitis.

S4C17P9-2: Another example of a lesion of PLVA shows the characteristic features of a lichenoid lymphocytic vasculitis. Focally, there is a parakeratotic cap. Perivenular infiltrates of lymphoid cells in the reticular dermis are prominent. There are collections of extravasated red blood cells at the dermal-epidermal interface. Just to the right of the center of the field, the thin epidermis shows increased cytoplasmic acidophilia; this is a degenerative change, and probably is evidence of early necrosis. In some areas, rete ridges are accentuated; in other areas, the rete ridges are effaced. The epidermal response is complex with both lichenoid and psoriasiform qualities; the combination might be characterized as pityriasic.


S4C17P9-3: In this example of PLVA, rete ridges (and the respective basal unit) are partially preserved. The short rete ridges have pointed extremities. There is preservation of a thin basal unit. The epidermal infiltrates of lymphoid cells are mostly confined to the altered basal unit. A parakeratotic cap is fairly uniform; focally, it contains clusters of degenerating neutrophils (munro microabscesses). There are prominent collections of red blood cells in the papillary dermis and the epidermis. The superficial unit shows pallor and intra-cellular edema.

S4C17P9-4: In this area of a lesion of PLVA, the basal unit is preserved; focally, it is hyperplastic. This feature sets the process apart from lichen planus-like reactions. Clusters of necrotic keratinocytes and whorls of regenerating keratinocytes, as seen in most erythema multiforme-like processes, are not a prominent feature. There is a loose cluster of degenerating cells just to the left of the ostium of a sweat duct (to the left of the center of the field).

S4C17P9-5: In this example of PLVA, clusters of extravasated red blood cells are present in the dermis, and the overlying epidermis. Lymphocytes and histiocytes form diffuse aggregates at the dermal-epidermal interface. Lesions of PLVA are characteristically rich in migratory histiocytes in both the epidermis and at the dermal-epidermal interface. The arrows identify some of the migratory histiocytes.

S4C17P9-6: In this field of a lesion of PLVA, blue arrows identify transformed T lymphocytes. Some degree of atypia in lymphoid infiltrates is acceptable in the setting of PLVA. The lesion is rich in migratory histiocytes; some of the histiocytes (red arrows) have been captured in transit across the basement membrane.

S4C17P9-7: This example of PLVA shows early epidermal necrosis. With the exception of a small area to the left of the center of the field, in which an island of the basal epidermal unit is partially preserved, the necrosis of the epidermis is full-thickness. There are focal collections of extravasated red blood cells in a defect at the dermal-epidermal interface.

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