Molecular Pathology - Malignant lymphoma

Question 1

Markers for T, B and NK cells

Answer 1

T cell = CD3 
- Helper T cell = CD4 
- Cytotoxic T cell = CD8
B cell = CD20 
NK cell = CD56

Question 2

Normal ratio of CD4 to CD8 T cells in lymphoid tissue?

Indication of skewed ratio?

Answer 2

CD4:CD8
1:1

Lymphoid tissue composed of mostly CD4 or CD8 indicates neoplasm - e.g. lymphoma

Question 3

Location of B-cell precursors and maturation in body?

Name one precursor B-cell neoplasm

Answer 3

Precursors at Bone marrow
Maturation at peripheral lymphoid tissue

B lymphoblastic leukemia/ lymphoma

Question 4

Location of T-cell precursors and maturation in body?

Name one precursor T-cell neoplasm

Answer 4

Precursors at Bone marrow and thymus
Maturation at peripheral thymus and peripheral lymphoid tissue

T lymphoblastic leukemia/ lymphoma

Question 5

4 major classes of lymphoma

Answer 5

Precursor lymphoid neoplasms

Mature B-cell neoplasms

Mature T and NK cell neoplasms

Hodgkin lymphomas

Question 6

Define lymphoid neoplasm.

How to distinguish between lymphoma and normal lymph node?

Answer 6

Clonal tumors of B, T or NK cells at various stages of differentiation
All cells in a lymphoma descend form one mutated cell with specific VDJ rearrangement of receptors/ Ig

> > Lymphoma = monoclonal, all share same VDJ arrangement
Lymph node = polyclonal, various VDJ arrangement

Question 7

Method of testing for lymphoma.

Answer 7

PCR on Ig or TCR genes

• B-cell lymphoma = share same VJ arrangement in Ig genes
• T-cell lymphoma = share same VDJ arrangement in TCR genes

Question 8

Compare Lymphoma tissue vs non-lymphoma tissue

• Clonality

Answer 8

• Clonality
  Lymphoma: monoclonal
  Non-lymphoma: polyclonal

Question 9

Compare Lymphoma tissue vs non-lymphoma tissue

• Ig/TCR arrangement
• PCR product of Ig/TCR genes
• Electrophoresis result

Answer 9

• Ig/TCR arrangement
  Lymphoma: Same V(D)J sequences in Ig/ TCR
  Non-lymphoma: varied
• PCR product of Ig/TCR genes
  Lymphoma: One single size
  Non-lymphoma: varied
• Electrophoresis result
  Lymphoma: single, sharp band
  Non-lymphoma: Smear pattern, range of products