Cytological diagnosis of malignant pleural effusion in myeloma.

The cytological examination of pleural fluid established the malignant etiology of the effusion in two patients with multiple myeloma. In contrast to patients with lymphoma, mediastinal lymph node enlargement in myeloma is an uncommon factor in fluid formation. As in patients with metastatic carcinoma, pleural and underlying lung involvement by myeloma is the main cause of pleural effusion. The two cases in this report, and similar cases in the literature, probably represent distal dissemination from skeletal multiple myeloma.