Syphilis is a sexually transmitted infectious disease, which currently shows a high increase of incidence in HIV negative patients. These patients Often seek medical advice at a stage of secondary syphilis, as the lesions of the primary phase may pass unperceived. Very often, the diagnosis is evoked through a cutoneous biopsy, since the clinical presentation is often misleading. Even though the histological signs are not specific, they may suggest the diagnosis, by showing a psoriosiform epidermal hyperplasio with neutrophil exocytosis and a dermal lichenoid infiltrate rich in plasma cells. However, it is important to underline the great polymorphism of these lesions, which con easily vary according to the stage and /or clinical form. It's very important to hove a quick and accurate diagnosis, because the lesions are very cantagious, but rapidly and completely cured by on early administrated antibiotic treatment.