Extramedullary Plasmacytoma

Primary extramedullary plasmacytoma occurs rarely and involves most commonly the upper air passages and paranasal sinuses (90%), though a variety of organ involvement has been reported.105 The clinical manifestations depend on the sites of involvement. In the head and neck region, painless or painful mass may be the first sign. Nasal obstruction, discharge, epistaxis, hoarseness, or hemoptysis may occur. Less commonly involved sites include lung, GI tract, lymph nodes, and the thyroid gland. Only about 20% of patients will have serum monoclonal proteins, and the bone marrow is not involved. Diagnosis is made by histologic or cytologic demonstration of myeloma cells in the biopsied specimen. Establishment of monoclonality, by specific antibody staining for cyto-plasmic immunoglobulin to show light-chain restriction or immunoglobulin gene rearrangement, is sometimes necessary to differentiate this entity from reactive plasmacytosis. A bone survey is necessary to exclude bone involvement, and magnetic resonance imaging (MRI) or 18F-fluorodeoxyglucose positron emission tomography (18F-FDG PET) may be used to detect other soft tissue involvement.106

More commonly, extramedullary plasmacytomas develop at the terminal phase of myeloma. A wide variety of organs have been shown to be invaded in postmortem examination.85 With increasingly effective chemotherapy, more patients develop extramedullary plasmacytoma during the late phase of their disease.

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