[Diffuse gingival plasmacytoma. Apropos of an case with an immunofluorescence and electron microscopy study].

A 5.1/2-year-old girl presented with an isolated diffuse gingival hypertrophy and an abnormal mobility of teeth (alveolysis on roentgenograms). The diagnosis of a plasmacytoma was suspected after pathological and immunohistological examinations of a gingival biopsy. Plasma cells were secreting monoclonal immunoglobulins (heavy chain IgA and light chain lambda), quite different from polyclonal secretions of a reactive plasmacytosis. The electron microscopic study demonstrated polymorphic plasma cells (well-differentiated, dysplastic or undifferentiated cells). The isolated nature of this tumor was confirmed by biological tests and radiological investigations. The extremely rare diffuse gingival locations of extraosseous solitary plasmacytomas was proved by a review of the published litterature. The evolution of such gingival tumors is unknown. It seems to be variable, and, perhaps, diffuse myelomas may develop later on (as in other sites of extra-osseous solitary plasmacytoma).