Massive Myelomatous Pleural Effusion With Contralateral Mediastinal Shift: A Unique Presentation of Extramedullary Myeloma.

Multiple myeloma (MM) is a relatively common malignancy that primarily affects the bone marrow, while extramedullary disease (EMD) occurs in the skin and muscle, lung pleura, lymph nodes, liver, and CNS. Myelomatous pleural effusion (MPE) is a rare extramedullary manifestation of MM in which pleural fluid is composed almost entirely of abnormal plasma cells. MPE and other types of EMD are associated with poor prognosis, and MPE can present emergently due to tension physiology. We report a case of a patient with massive MPE presenting with contralateral midline shift. There are exceedingly few such cases and this report highlights a unique presentation of this rare clinical entity. Epidemiology, radiographic features, diagnosis, treatment, and implications for the prognosis of the disease are discussed.