The Histopathological Features of Secondary Syphilis: A Case Series

Secondary syphilis has a wide range of clinicopathological presentations. Diagnosis is aided by detection of spirochetes in tissue or serologic studies. Here, we describe histopathological features of a series of cases of secondary syphilis at our institution to assess if any patterns are typical of cases with positive spirochete immunohistochemistry.

A search of our dermatopathology database from 2016 to 2023 was performed for cases of secondary syphilis. Available H&E-stained slides, spirochete immunohistochemistry, and patient information were reviewed.

Thirty-three biopsies from 27 patients were included. Four epidermal reaction patterns were observed, with acanthosis (36.4%), a flattened epidermis (21.2%), and normal epidermis (18.2%) being the most common changes. Granulomas were present in 42.4%, and eosinophils were noted in 18.2%. 87.9% of specimens had plasma cells. Six dermal reaction patterns were identified. 39.4% showed vacuolar interface changes without prominent inflammation, while 18.2% showed lichenoid inflammation. 81.8% of samples stained positive for spirochetes.

Although secondary syphilis is typically thought to have elongated rete with a lichenoid infiltrate with plasma cells, there is a broad range of possible epidermal and dermal inflammatory cells and reaction patterns. Secondary syphilis should be considered for a wide spectrum of inflammatory disease.