What sample is recommended for diagnosing splenic marginal zone lymphoma (SMZL) with a NOTCH2 mutation?

Diagnostic Samples for SMZL with NOTCH2 Mutation

For diagnosing splenic marginal zone lymphoma (SMZL) with a NOTCH2 mutation, a combination of peripheral blood and bone marrow samples is recommended as the first-line diagnostic approach, with splenectomy specimen reserved only for cases where diagnosis remains uncertain. 1

Primary Diagnostic Samples

First-line Samples

• Peripheral blood

  • Complete blood count with differential
  • Peripheral blood smear for morphological examination (looking for villous lymphocytes)
  • Flow cytometry of peripheral blood (mandatory) 2

• Bone marrow

  • Bone marrow aspirate for morphology and flow cytometry
  • Bone marrow biopsy for histology and immunohistochemistry (IHC)
  • Look for characteristic intrasinusoidal infiltration pattern by CD20+ cells 1

Molecular Testing on Blood/Bone Marrow

• NOTCH2 mutation testing (specific for SMZL) 3
• FISH studies for deletion of 7q (almost specific for SMZL) 1, 4
• MYD88 mutation testing (should be negative in SMZL) 2

Second-line Sample (if diagnosis remains uncertain)

• Splenectomy specimen 2, 1
  • Required in a minority of cases (approximately 10-15%)
  • Provides definitive diagnosis through histopathological examination
  • Allows visualization of characteristic micronodular tumoral infiltration with marginal zone differentiation 5

Immunophenotyping Profile to Look For

• Positive markers: CD19, CD20, CD22, CD79a
• Negative markers: CD5 (usually), CD10, CD23, CD43, cyclin D1
• Variable expression: CD103, CD11c, CD25 1, 6

Diagnostic Algorithm

1. Start with peripheral blood and bone marrow samples
2. Perform flow cytometry and immunophenotyping
3. Test for NOTCH2 mutations and 7q deletion
4. If diagnosis remains uncertain after these tests, consider splenectomy

Important Considerations

• NOTCH2 mutations are almost specific biomarkers for SMZL, present in approximately 10-25% of cases 3, 5
• The combination of peripheral blood/bone marrow examination is sufficient for diagnosis in most cases 2
• Splenectomy should be avoided when possible due to associated morbidity, and reserved only for cases where diagnosis cannot be established through less invasive methods 1
• In aggressive variants of SMZL, additional molecular testing beyond NOTCH2 may be warranted 7

Pitfalls to Avoid

• Do not rely solely on peripheral blood morphology, as villous lymphocytes are not seen in all cases of SMZL 2
• Do not mistake SMZL for other B-cell lymphomas with similar presentations (hairy cell leukemia, lymphoplasmacytic lymphoma, chronic lymphocytic leukemia) 6
• Do not automatically proceed to splenectomy without first attempting diagnosis through peripheral blood and bone marrow samples 1