Which histologic findings are characteristic of papular urticaria?

Updated: Feb 12, 2021
  • Author: Robert A Schwartz, MD, MPH; Chief Editor: Dirk M Elston, MD  more...
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In a prospective study of papular urticaria that evaluated the histopathologic features of 30 affected patients, more than 50% of patients had mild acanthosis, mild spongiosis, exocytosis of lymphocytes, mild subepidermal edema, extravasation of erythrocytes, superficial and deep mixed inflammatory cell infiltrate of moderate density, and interstitial eosinophils. [15] Immunohistochemical analysis revealed abundant T lymphocytes (CD45RO, CD3) and macrophages (CD68). B lymphocytes (CD20) and dendritic antigen-presenting cells (S100) were not seen. [15] Direct immunofluorescence staining did not demonstrate immunoglobulin A (IgA), immunoglobulin G (IgG), IgM, C3, or fibrin.

The occasional overlapping in histologic pattern between papular urticaria exhibiting the histologic features of pseudolymphoma and a true lymphoma can cause problems. Persistent nodules may suggest the possibility of a lymphoma, not papular urticaria, and require a skin biopsy specimen.

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