Syphilis, known as "the great mimicker," is caused by the spirochete Treponema pallidum and is characterized by a diverse array of clinical and histopathologic presentations. In secondary cutaneous syphilis, the most consistent morphological features include a superficial and deep perivascular infiltrate containing plasma cells, varying degrees of endothelial swelling, irregular acanthosis, elongation of rete ridges, a vacuolated pattern, and the presence of plasma cells. Although serologic tests are essential for definitive diagnosis, spirochetes can sometimes be directly identified in silver-stained tissue slides or through immunohistochemistry. Granuloma annulare is a relatively common, benign, self-limiting condition with 3 main variants: conventional, subcutaneous, and interstitial, each with distinct characteristics. In this study, we report 2 cases of cutaneous secondary syphilis with a striking granulomatous reaction pattern that closely mimics the interstitial variant of granuloma annulare. Owing to the severity of the tertiary stage of syphilis, distinguishing between these 2 entities is crucial.

Bioptic Laboratory Ltd Pilsen Czech Republic

Department of Pathology Faculty of Medicine in Pilsen Charles University Pilsen Czech Republic

Department of Pathology ULS Gaia e Espinho Vila Nova de Gaia Portugal

Dermatology Prof Hercogova Prague Czech Republic

Dermskin Ltd Olomouc Czech Republic; and

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