Surgical Pathology Criteria

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

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