Lymphoplasmacytic Lymphoma

WHO classification:

• Small B cell lymphoma which does not fulfill criteria for other small B-lymphoid neoplasms
• Waldenstrom’s macroglobulinaemia is specific subset of LPL with an IgM paraprotein and bone marrow involvement

Morphological features:

• Small, pleomorphic and plasmacytoid
• May have eccentric nuclei or cytoplasmic basophilia
• Plasma cells may be seen circulating
• Rouleux formation (paraprotein)
• Increased background staining (paraprotein or cryoglobulinaemia)

Other features to look out for:

• RBC agglutination
• Cryoglobulin deposits

Differential diagnosis:

• Marginal zone lymphoma
• Plasma cell leukaemia
• Chronic lymphocytic leukaemia
• Mantle cell lymphoma

Investigations:

• Flow cytometry: non-specific phenotype, but often CD38+/5-/23-/10-/123-
• Serum immunofixation for detection of paraprotein
• MYD88 mutation seen in >90% of LPL, but it is neither sensitive nor specific, and is not required for diagnosis