IgG myeloma presenting as a large mediastinal mass and pleural effusion.

Plasmacytoma, a rare form of plasma cell dyscrasia, refers to a neoplastic proliferation of plasma cells. Although the upper aerodigestive tract is the most common site for extramedullary plasmacytoma, mediastinal and pleural involvement is extremely rare. We report the case of a patient who presented with a large mediastinal mass and pleural effusion. Diagnosis was challenging and subsequently made as mediastinal extramedullary plasmacytoma with simultaneous myelomatous pleural effusion. Further investigations revealed multiple myeloma.