ABSTRACT
Multiple myeloma is a neoplasm of mature and immature plasma cells. Extraosseous tissues are involved frequently in multiple myeloma. The most common sites of involvement are spleen, liver, lymph nodes, and kidneys. Sinus involvement of multiple myeloma is rare but usually presents in secondary extramedullary plasmacytoma. Primary extramedullary plasmacytoma is neoplastic proliferation of plasmacytes in reticuloendothelial tissues and occurs most commonly in head and neck areas. Evaluation of the extent of disease is essential for proper management of this patient. The treatment and prognosis are different according to whether the extramedullary plasmacytoma is primary or secondary. Recently, we experienced a case of multiple myeloma which simultaneously progressed in maxillary sinus in spite of systemic chemotherapy and report with literature review.