Unilateral pleural effusion as a presenting manifestation of plasma cell myeloma (multiple myeloma): a case report.

Background malignant pleural effusion caused by multiple myeloma (MM) is rare, occurring as a late complication with a poor prognosis. Myelomatous pleural effusion (MPE) as an initial manifestation of the disease is extremely uncommon. Case A 54-year-old, previously healthy man presented with right-sided pleural effusion. Cytologic examination of the aspirated fluid revealed large, slightly pleomorphic atypical cells, some having eccentric nuclei. Immunocytochemistry (ICC) performed on cytospin smears and cell block sections gave a positive reaction for CD1 38, EMA and vimentin and a negative reaction for CK7, CK20, calretinin, S-100 and E-cadherin. Conclusion Cytopathologists may be caught unawares by atypical presentations of hematologic malignancies. The diagnosis of MPE requires a high level of suspicion, and routine incorporation of ICC in the cytologic evaluation will ensure accurate diagnosis and proper patient management.