Plasma Cell Myeloma
Supplemental Studies
Immunohistology and Flow
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Plasma cell quantitation is performed by differential count on the bone marrow aspirate or by immunohistochemistry for CD138 on the bone marrow biopsy
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Flow cytometry may significantly underestimate plasma cell percentage
- It does establish clonality and can differentiate residual clonal plasma cells from admixed polytypic plasma cells
Hematolymphoid markers
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CD45 absent or dim in >99%
B cell and plasma cell markers
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CD138 >99%
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CD38 >99%
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CD79a, most
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CD20 variable, often absent
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CD19 variable, often absent
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CD56 up to 80% -- aberrant antigen
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Cytoplasmic kappa or lambda light chain by flow cytometry, in situ hybridization, or immunohistochemistry
Other
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Cyclin D1 (Bcl1) positive plasma cell myelomas often lymphoplasmacytic, CD20+, have better prognosis
Cytogenetics
- Loss of 13q14
- Most common abnormality
- Associated with poor prognosis
- t(11:14)(q13:q32)
- Associated with:
- Cyclin D1 overexpression
- Lymphoplasmacytic or small lymphocytic morphology
- Better prognosis
Useful Laboratory Tests
- Serum or urine protein electrophoresis, immunofixation, light chain quantification
- Quantitation and typing of monoclonal immunoglobulin / light chain
- Serum free light chain analysis may be required to demonstrate clonal light chains
- These studies may be used to
- Establish presence of a monoclonal plasma cell population
- Quantitation helps subtype the plasma cell dyscrasia (i.e. >3g/dL serum monoclonal protein is a major criterion for myeloma)
- Track disease burden over time
Plasma cell leukemia
- Frequently CD20+, CD56-, t(11;14)+
- Frequently unusual M component (non-secretory, IgD, IgE, light chain only)
