Intraoral primary syphilis mimicking lymphoproliferative disorder

Syphilis can mimic, clinically and microscopically, many other diseases. By microscopy, typically syphilis presents with plasma cell infiltration, admixed with lymphocytes and macrophages, in lichenoid and/or perivascular/perineural distribution pattern. When exuberant, this inflammatory infiltrate can mimic a lymphoproliferative disorder (LPD), notably plasma cell neoplasia or lymphoma. To date, about 12 cases of secondary syphilis, all but one in extraoral location, suggesting initially a LPD, have been published. Here, to our knowledge, we report an unusual case of intraoral primary syphilis initially suggesting LPD, notably lymphoid hyperplasia (pseudolymphoma); however, mucosa-associated lymphoid tissue (MALT) lymphoma and follicular lymphoma could not be disregarded. Polyclonality of plasma cells on immunohistochemistry, in strict clinical correlation, was essential to arrive at the correct diagnosis.