Syphilis of the Aerodigestive Tract.

Syphilis, a sexually transmitted infection caused by the Gram-negative bacterium Treponema pallidum, is increasing in prevalence in the United States. It has been our experience that primary and secondary syphilis of the aerodigestive tract can afflict a large age spectrum with varied clinical and histopathologic findings, which can lead to diagnostic problems and frequent misdiagnosis. In this study, we describe the histopathologic patterns of syphilis of the aerodigestive tract to expand awareness of its varied appearance. We identify 3 patterns of inflammatory response to syphilis: plasma cell-rich, lymphohistiocytic, and lymphoma-like. We also report the presence of immunoglobulin G4-predominant plasma cells in the inflammatory response as a potential mimicker of immunoglobulin G4-related disease. Lastly, we found that use of T. pallidum immunohistochemical stain is more reliable than Steiner silver stain at the identification of spirochetes. Our study highlights that despite convention, plasma cells are not always abundant in syphilis. Awareness of the histopathologic range of syphilis in the aerodigestive tract by the surgical pathologist can lead to the correct diagnosis and guide appropriate treatment.