IgM multiple myeloma: Pathologic evaluation of a rare entity

Rebecca L. King, Matthew T. Howard, Janice M. Hodnefield, William G. Morice

Research output: Contribution to journalArticlepeer-review

20 Scopus citations


Objectives: To delineate the pathology of immunoglobulin M-producing multiple myeloma (IgM MM). Methods: Clinicopathologic data were reviewed for 15 cases meeting World Health Organization criteria for MM and having a serum IgM paraprotein. Immunohistochemistry was performed on diagnostic bone marrow specimens for common B-cell and plasma cell markers. Results: Of the 15 IgM MM bone marrows reviewed, 6 (40%) had lymphoplasmacytoid cytology, and 12 (80%) expressed CD19, CD20, and/or CD45. Cyclin D1 expression was common (11 cases, 73%) and usually associated with t(11;14). No cases expressed CD5 or had an associated CD5-positive B-cell population. CD117 was positive in 20% of cases. Conclusions: The frequent B-cell-associated antigen expression by IgM MM distinguishes it from other MM types, causing significant pathologic overlap with lymphoplasmacytic lymphoma (LPL). However, IgM MM is usually distinguished from LPL by aberrant cyclin D1 expression or t(11;14). Therefore, assessing for these abnormalities is recommended when evaluating bone marrow involvement by IgM-associated lymphoplasmacytoid disorders.

Original languageEnglish (US)
Pages (from-to)519-524
Number of pages6
JournalAmerican journal of clinical pathology
Issue number4
StatePublished - Oct 2013


  • Cyclin D1
  • IgM multiple myeloma
  • Immunophenotype
  • Lymphoplasmacytic lymphoma
  • Pathology

ASJC Scopus subject areas

  • Pathology and Forensic Medicine


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