Immunostaining a bone marrow specimen with CD56 can help to distinguish multiple myeloma with lytic bone lesions from other conditions with increased plasma cells in the bone marrow.
Patient selection: increased plasma cells in the bone marrow (may be identified by immunostaining for CD138)
CD56 = Neural Cell Adhesion Molecule (NCAM)
Staining with CD56
Diagnosis
equal to or greater than staining of osteoblasts
multiple myeloma with lytic bone lesions
negative or very weak
reactive plasmacytosis
monoclonal gammopathy of undetermined significance
malignant lymphoma with plasmacytoid differentiation (lymphoplasmacytoid lymphoma, Waldenstrom's MG)
multiple myeloma without lytic bone lesions
where:
• Positive immunostaining of osteoblasts by CD56 serves as an internal control.
• Plasma cells in myeloma will also so monoclonal expression of kappa or lambda light chains.
• Plasma cells in myeloma with lytic bone lesions may also be cyclin D1 positive.
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