CD5-CD10- B-cell lymphomas: Lymphoplasmacytic lymphoma:
Bone marrow sample: MYD88+(*)
* MYD88 is a useful marker for lymphoplasmacytic lymphoma, although it is not strictly necessary for the diagnosis and is not specific for this entity (see Xinfang et al. Cancer Res 2018;78:2457-2462 for more information).
Plasma cells were not detected by flow cytometry in this sample (note plasma cell enumeration by flow cytometry is unreliable), but were present by IHC with IgM expression and lambda restriction. In plasmacytic differentiation of B-cell neoplasms, the plasma cells typically show light chain restriction with otherwise normal phenotype (retained CD45 and CD19 expression).
Bone marrow sample: MYD88+ : This case was interesting because the myeloma tubes were performed as well (see section on plasma cell neoplasms for more detailed information on markers useful for the assessment of plasma cells). Remember that in plasmacytic differentiation of B-cell neoplasms, the plasma cells typically show light chain restriction with phenotype otherwise within normal limits (retained CD45 and CD19 expression).
Both B-cells and plasma cells show Immunoglobulin light chain Kappa restriction.
Plasma cells show preserved expression of CD81 and CD27. They do not show aberrant expression of CD117 or CD56.
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