Which findings on immunochemistry are characteristic of plasma cell lesions?

Updated: Oct 14, 2019
  • Author: Lesley Elizabeth Fox, MD; Chief Editor: Francis H Gannon, MD  more...
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Immunophenotypic features of plasma cell myeloma and solitary plasmacytoma of bone are similar. Immunophenotyping by flow cytometry may show an aberrant clone of plasma cells with the following phenotype: CD45-, CD79a+, CD19+, CD38+, CD138+ with monoclonal expression of cytoplasmic light chains. More than 50% of cases will express CD43, CD117, and/or CD56. Aberrant expression of CD20, CD10, and CD52 is seen to a lesser degree. [1, 4]

An important consideration is the frequent underestimation of plasma cells by flow cytometry. As such, immunohistochemical stains may be necessary in problematic cases (see the following images). [12] Differential diagnosis by immunophenotype includes, but is not limited to, the following [1, 4] :

  • Reactive plasma cell proliferations

  • Lymphoplasmacytic lymphoma

  • Plasmablastic lymphoma, lymphomas with plasmablastic or plasmacytoid features

  • Nonlymphoid malignancies with CD56 expression (acute myeloid leukemia, carcinoma)

    Immunohistochemistry is useful in demonstrating th Immunohistochemistry is useful in demonstrating the clonality of the lesion. Occasionally, the stains can be hard to interpret, but in general, either the kappa (pictured here) or the lambda light chain will show positivity. If both stains are positive, a tumor diagnosis should be questioned.
    Immunohistochemistry for lambda light chains is in Immunohistochemistry for lambda light chains is intensely positive, and in the presence of a negative kappa light chain stain, helps in the identification of the diagnosis.

Correlation of the immunophenotype with clinical, radiologic, and morphologic features will aid in distinguishing these entities from plasma cell myeloma or solitary plasmacytoma of bone, as well as in distinguishing plasma cell myeloma from solitary plasmacytoma of bone.

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