IgM myeloma: Case report with immunophenotypic profile

• Published in: American journal of hematology Vol. 59; no. 4; pp. 302 - 308
• Main Authors: Haghighi, Bijan, Yanagihara, Ronald, Cornbleet, P. Joanne
• Format: Journal Article
• Language: English
• Published: New York Wiley Subscription Services, Inc., A Wiley Company 01.12.1998; Wiley-Liss
• Subjects: Aged; Aged, 80 and over; Antigens, Differentiation, B-Lymphocyte - analysis; Antigens, Neoplasm - analysis; Biological and medical sciences; Bone Marrow - pathology; Female; Flow Cytometry; Fractures, Spontaneous - etiology; Humans; IgM; Immunodeficiencies. Immunoglobulinopathies; Immunoenzyme Techniques; Immunoglobulin M - analysis; Immunoglobulinopathies; Immunopathology; Immunophenotyping; Lymphocyte Activation; lymphoproliferative disorders; Medical sciences; multiple myeloma; Multiple Myeloma - classification; Multiple Myeloma - complications; Multiple Myeloma - metabolism; Multiple Myeloma - pathology; Myeloma Proteins - analysis; Neoplastic Stem Cells - chemistry; Waldenstrom Macroglobulinemia - classification; Waldenstrom Macroglobulinemia - metabolism; Waldenstrom Macroglobulinemia - pathology; Waldenström's macroglobulinemia; Human; Immunopathology; Flow cytometry; Clinical form; Malignant hemopathy; Myeloma; IgM; Case study; Phenotype; Immunoglobulinopathy; Immunological investigation; Lymphoproliferative syndrome; Female; Waldenstrom macroglobulinemia; Elderly
• ISSN: 0361-8609; 1096-8652
• DOI: 10.1002/(SICI)1096-8652(199812)59:4<302::AID-AJH6>3.0.CO;2-Z

Immunoglobulin (Ig)M myeloma is a distinct subtype of multiple myeloma (MM) displaying clinical and pathologic features of both MM and Waldenström's macroglobulinemia (WM). Although the immunophenotypic characteristics of classic MM and WM have been reported, the surface antigen expression of IgM myeloma has not been reported. We report a case of IgM myeloma and describe its immunophenotypic profile using flow cytometry. The cells showed a hybrid MM‐WM phenotype, strongly expressing CD38 but lacking CD45 and DR, typical for plasma cells; however, pan‐B cell antigens CD20 and FMC7 as well as weak monoclonal surface Ig also were positive, resembling B‐cell lymphoproliferative malignancies. Discordant B‐cell antigen expression was present, in that pan‐B antigens CD19 and CD22 were absent. In addition, B‐cell activation antigen CD23, early B‐precursor antigen CD10, and pan‐T antigen CD5 were not expressed. Although CD20 and weak surface Ig expression have been reported in MM, FMC7 positivity has not been seen. The data therefore suggest that IgM myeloma may have a unique phenotype with characteristics of both MM and WM. Am. J. Hematol. 59:302–308, 1998. © 1998 Wiley‐Liss, Inc.