Abstract

Syphilis, “the great mimicker,” is resurgent and requires vigilance from pathologists and clinicians. Robust CD30 positivity in the inflammatory infiltrate of syphilis is sparsely described. We recently encountered a case of syphilis in which the biopsy had a brisk epidermotropic lymphocytic infiltrate that was initially categorized as an “atypical lymphoid infiltrate,” suggestive of lymphoma. The biopsy showed a dense lymphohistiocytic infiltrate, interface changes, prominent intra-epidermal scattering of inflammatory cells, marked CD30 positivity, and few plasma cells. The diagnosis of syphilis was made after a delay, when the clinical picture became more suggestive and immunohistochemical stain for T. Pallidum revealed numerous spirochetes. We performed a retrospective study of syphilis cases from the last year (7 total patients) for the presence of CD30 staining. Including the index case, one additional biopsy (total 2 of 7) showed dramatic staining for CD30. All other specimens exhibited some staining, although to lesser degree. Many of the CD30 positive cells had dendritic cytoplasms. The two cases with brisk CD30 positive infiltrate were further studied with dual chromogen stains with CD30 and CD3, CD4, CD8, factor 13a, S100, and CD1a. The CD30 positive cells showed variable co-staining with CD4 and CD8 or none. None of the CD30 positive cells co-stained with factor 13a, S100, or CD1a. Syphilis should be included in the differential of cutaneous lesions that may have many CD30-positive cells. The CD30 positivity seems to be present in a variety of T-cells and histiocytes in the inflammatory response to T. Pallidum infection.

Financial Disclosure:
No current or relevant financial relationships exist.