[Cutaneous plasmacytoma: review of the literature apropos of a case].

Extramedullary plasmocytomas are ubiquitous plasmocytic tumours which are principally located in bones and mucosae but rarely found on the skin. Clinically, they present as purplish-blue cutaneous nodules or, less frequently, as papular or urticarial eruptions. The diagnosis rests on histology and immunostaining. Cutaneous plasmocytomas are usually divided into two types: (1) primary plamocytomas which occur in the absence of myeloma, present as solitary or multiple skin tumours, accompanied or not by monoclonal gammopathy, and have an imperfectly known course and prognosis; (2) secondary plasmocytomas--a case of which is reported here--which appear in the course of a large tumoral mass myeloma and have a very poor prognosis.