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Case of the Month: August 2022

posted: August 24, 2022

A 51-year-old male with history of high-risk IgG Lambda multiple myeloma with multiple lytic bone lesions (C7, T4, left side manubrium, right distal humerus, right maxillary tuberosity, and right femur), positive for monosomy-13 and FGFR3/IGH fusion t(4;14) on FISH, who presents with massive left pleural effusion (1150 ml). The ThinPrep and section of the cell block from pleural effusion are shown below.

Pleural Effusion ThinPrep (Papanicolaou stain) and cell block (H&E stain)
Figure 1
Figure 1
  • BER-EP4
  • MOC31
  • CD138
  • Mum1
  • Lambda ISH
  • Kappa ISH

Additional immunostains results: Cyclin D1 is focally positive in the tumor cells; Calretinin is negative.

Figure 2
Figure 2
View Final Diagnosis
Final Diagnosis: Myelomatous Pleural Effusion (MPE)
The specimen is composed mostly of malignant plasma cells with abundant cytoplasm and eccentrically placed nuclei as well as binucleated forms (examples indicated by arrows) in a background of reactive mesothelial cells. The malignant cells are diffusely and strongly immunoreactive for CD138 and Mum1, with Lambda light chain restriction by ISH, confirming monoclonal proliferation; negative for epithelial markers (BER-EP4 and MOC31) and mesothelial marker (Calretinin). Flow cytometry results demonstrate the presence of a clonal population of cells which are immunophenotypically consistent with plasma cells neoplasm.
In view of the patient’s history of high-risk IgG Lambda multiple myeloma with multifocal bone involvement, the cytomorphology, immunoprofile, and flow cytometry are compatible with myelomatous pleural effusion (MPE).
Plasma cell myeloma/multiple myeloma (PCM/MM) is a bone marrow-based, multifocal neoplastic proliferation of plasma cells. The etiology of PCM/MM is unknown but is believed to represent a combined effect of genetic susceptibility and environmental exposures. PCM/MM rarely involves the serous cavities. The pleura is involved more commonly than the peritoneum or pericardium. Pleural effusion (PE) is not an uncommon finding, present in 6-14% of patients with PCM/MM, but only <1% of patients present as MPE. The most common cause of PCM/MM associated PE are congestive heart failure, renal failure with or without nephrotic syndrome, parapneumonic effusion, and amyloidosis. The diagnostic workup of MPE includes cytologic examination with ancillary studies (Immunohistochemistry, Kappa/Lambda ISH, etc.), flow cytometry, protein electrophoresis with immunofixation, pleural biopsy, and clinical features.
  1. WHO Classifications of Tumors: Hematolymphoid Tumors. 5th Edition
  2. Pleural effusion and multiple myeloma – more than meets the eye: A case report. Molecular and Clinical Oncology. 2021; 15: 238.
  3. Massive pleural effusion due to IgG-Kappa subtype multiple myeloma: A case report. Respiratory Medicine Case Report. 2020; 29.
  4. Clinicopathological profile of myelomatous pleural effusion: Sigle-center real-world experience and review of literature. Clinical lymphoma, Myeloma & Leukemia. 2018; 19: 183-9.

This case is contributed by Dr. Qun Wang (Emory University Hospital, Department of Pathology).