[Extramedullary anaplastic plasmacytoma].

A case of extramedullary plasmacytoma of the maxillary sinus, locally aggressive, in a 65 years old man is presented. Clinical diagnosis of adenocarcinoma was suspected but the pathological study showed an anaplastic morphology, with little plasmacytic differentiation and lack of stain with cytokeratins and epithelial membrane antigen (EMA), immunohistochemical marker of plasmatic cells, among others. Definitive diagnosis was based on light chain restriction and lack of multiple myeloma.