The authors present a case of synchronous manifestation of a myeloproliferative--extramedullary plasmocytoma--and a chronic inflammatory disease of the nose and the paranasal sinuses. They emphasise the importance of imaging techniques and immunohistochemistry in the differential diagnosis. They discuss on the basis of published articles the new classification, clinical manifestations, diagnostic and therapeutical approaches of this tumour belonging to the group of monoclonal gammopathies, which originates from an abnormal proliferation of mature B-lymphocytes, and is a rarity in the literature even nowadays.