Plasmacytoma
Differential Diagnosis
Plasmacytoma |
Myeloma |
Single osseous or extraosseus lesion |
Lytic bony lesions |
No increase away from lesion |
Usually increased plasma cells on random bone marrow biopsy |
No end-organ damage |
May have end-organ damage |
Plasmacytoma / Myeloma |
Reactive Plasmacytosis |
Light chain restriction by flow cytometry, immunohistochemistry or in situ hybridization |
No light chain restriction |
Plasmablastic Lymphoma |
Anaplastic (Plasmablastic) Plasmacytoma/Myeloma |
Plasmablastic morphology |
Subset plasmablastic |
Often HIV+ or otherwise immunosuppressed |
Usually not immunosuppressed |
Often in oral cavity or mucosal areas of head |
Extraosseous sites overlap |
~60% EBV+ |
usually EBV negative |
Plasmacytoma and plasmablastic lymphoma have the same immunophenotype, other than EBV and are generally separated based on clinical grounds
Plasmacytoma / Myeloma |
Lymphoplasmacytic Lymphoma and Nodal, Extranodal and Splenic Marginal Zone Lymphomas |
Plasma cells may be pleomorphic or plasmablastic |
Plasma cell component usually not markedly atypical |
Uniform plasma cell morphology |
Plasma cells mixed with small lymphocytes |
IgG or IgA M component most common |
IgM or IgG M component most common |
CD20 often negative |
CD20 80% |
Uniformly CD138 positive |
Scattered CD138 positive cells |
Often CD56+, CD19-, CD45- |
CD56-, CD19+, CD45+ |
ALK Positive Large B Cell Lymphoma |
Plasmacytoma |
ALK positive |
ALK negative |
Often involves nodes in sinusoidal pattern |
No sinusoidal node involvement |
Usually presents with adenopathy without lytic bone lesions |
Usually presents with lytic bone lesions without adenopathy |
No M component |
May have M component |
May show ALK-clathrin translocation t(2;17)(p23;q23) |
Lacks this translocation |
Both may have basophilic cytoplasm with a perinuclear hof
Primary Effusion Lymphoma |
Plasmacytoma |
HHV8 positive |
HHV8 negative |
EBV in situ positive |
EBV in situ infrequently positive |
Most patients HIV positive |
No significant HIV predilection |
Usually presents as malignant effusion |
Usually presents as lytic bone lesion |
PEL may rarely occur outside of body cavities; both may have plasmablastic appearance