Penile mass with a past: Tertiary syphilis presenting as a penile gumma

A 46-year-old man presented with a rapidly growing, verrucous penile mass with bilateral inguinal lymphadenopathy, clinically consistent with locally advanced penile carcinoma. He had no history of sexually transmitted infections and negative rapid plasma reagin (RPR) testing. Biopsy demonstrated no malignancy, but immunohistochemistry revealed <i>Treponema pallidum</i>. He was diagnosed with tertiary syphilis and penile gumma. He was treated with penicillin G, though the gumma showed minimal response and surgical extirpation was recommended. This case highlights the limitations of traditional RPR-first screening in syphilis and underscores the importance of a broad differential diagnosis when addressing penile masses.