Which histologic findings are characteristic of pityriasis lichenoides?

Updated: Sep 11, 2020
  • Author: Jeffrey P Callen, MD; Chief Editor: Dirk M Elston, MD  more...
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Ackerman has established histopathologic criteria for fully developed lesions of PLEVA and PLC. [32] Early lesions in both variants are smooth, since areas of parakeratosis initially are overlain by a normal cornified layer with a basket-woven appearance.

PLEVA lesions are characterized by a wedge-shaped superficial and deep dermal lymphohistiocytic infiltrate with intravascular margination of neutrophils, a confluent parakeratotic scale crust, thinning of the granular layer, basilar necrosis of keratinocytes, vacuolar interface dermatitis with a lymphocyte in nearly every vacuole, erythrocyte extravasation, and dermal edema.

Rare cases of γδ T-cell–predominant disease may mimic more aggressive lymphomas histologically. [33, 34]

PLC lesions are characterized by a superficial dermal infiltrate, focal parakeratosis, preservation of the granular layer, and focal disappearance of the dermal-epidermal interface.

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