Morphological features:
- Small atypical lymphoid cells
- Lacks uniform appearance of CLL (mildly pleomorphic)
- Mature nuclei, sometimes may have inconspicious nucloeli
- Prominent nucleoli are uncommon, more seen in hairy cell variant
- Scanty, weakly basophilic cytoplasm
- Occasional lymphocytes may appear lymphoplasmacytoid
- Splenic lymphoma with villous lymphocytes (SMZL in blood) will have polar villous margins
- Projections may also be multiple, resembling variant hairy cell leukaemia
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Other features to look for:
- Rouleux, indicating paraprotein formation
- Haemolytic anaemia (spherocytes / agglutination) – first slide below
- Post-splenectomy features – second slide below
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Differential diagnosis:
- Chronic lymphocytic leukaemia
- Mantle cell lymphoma
- Hairy cell variant
- Lymphoplasmacytic lymphoma
| Disease | Immunophenotype | Other Features |
|---|---|---|
| Hairy cell leukaemia | 20++/11c+/25+/103+/123+ | Annexin A1 positive BRAF positive Monocytopaenia Pancytopaenia |
| Hairy cell variant | 20+/11c+/103+/25-/123- | No monocytopaenia Generally high WBC May have prominent nucleoli BRAF mutation negative Annexin A1 and TRAP negative 50% have TP53 abnormalities and MAP2K1 mutations |
| Splenic marginal zone leukaemia / Splenic lymphoma with villous lymphocytes | Non-specific B cell phenotype. May be 11c+, occasionally 5+ or 103+. |
Investigations
- Flow cytometry usually shows a non-specific phenotype: 20+/10-/sIgM+/103-/11c+/25-/23-/10-/5variable (see here)
- Serum immunofixation may show a paraprotein
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