T- cell lymphoproliferative disorders Flashcards
What immunophenotype do cortical T thymocytes have?
- cytoCD3+, CD5+, CD7+, CD4+, CD8+, TdT+, CD1a+
What immunophenotypic features are associated with gamma delta T cell lymphoma?
- Lack of expression of CD4, CD8 and CD5
What immunophenotypic features are associated with the follicular helper T cell subset?
- CD4+, CD10+, BCL-6+, CD57+ , CXCR5+, PD-1+
- Secrete CXCL13 (receptor= CXCR5), IL4 and IL21
What T cell disorders can be CD4+ and CD8+
- Cortical thymocyte T-ALL
- T-PLL
What T cell disorders can be CD4- and CD8-
- Hepatosplenic T cell lymphoma
- EATL
- Some anaplastic T cell lymphomas
- (NK lymphoma/ leukaemia)
Expression of what two genes has been proposed as being important in the delineation of different subtypes of peripheral T cell lymphoma NOS
1) GATA3 (Th2 cells, worse prognosis, more monotonous/ sheet-like)
2) TBX21/ T-BET (Th1, better prognosis, more heterogenous with an inflammatory background)
What is the “null-cell phenotype” in anaplastic T cell lymphoma and how can it be distinguished from HL?
- Refers to the loss of the pan T cell antigens
- Can be difficult to distinguish from HL as both are CD30+
- In anaplastic T cell lymphoma: CD15 usually -ve, PAX5-, EBV-. May be ALK+. Granzyme and TIA positive.
- In Hodgkin’s: LMP1 positive
What are the four histological subtypes of anaplastic T cell lymphoma?
1) Common pattern
2) Lymphohistiocytic
3) Small cell pattern
4) Hodgkin-like
What are the four subtypes of anaplastic T cell lymphoma
1) ALK+ (good prognosis)
2) DUSP22+ (good prognosis)
3) TP63+ (bad prognosis)
4) Triple negative (prognosis in between DUSP22 and TP63+)
What are the morphological features of angioimmunoblastic T cell lymphoma?
- Polymorphous infiltrate with atypical T cells, plasma cells, histiocytes, eosinophils.
- T cells have T helper follicular phenotype with 2 or more of: CD10, CXCR5, CXCL13, ICOS, PD1
- Expanded FDC network
- Large B cells in the background that are CD20 and EBV +
- Arborising venules.
What mutations/ gene fusions are seen in angioimmunoblastic T cell lymphoma?
- Mutations in TET2, DNMT3A, IDH2, RHOA, CD28
- Gene fusions in ITK-SYK, CTLA4- CD28
What is the immunophenotype of T-LGL?
CD3+, CD8+, C16+, CD57+
Diminished expression of CD5 and/or CD7
TIA, granzyme B positive
What genetic aberrations are typically seen in T-PLL?
- Overexpression of TCL1, caused by genetic rearrangements that bring the TCL1 gene under the control of the TRA
- inv(14) in 80%, t(14;14) in 10%
- MTCP1 (a homologue of TCL1) is located on the X chromosme
- t(X;14) in <10%
TCL1 and MTCP1 alterations enhance cell proliferation and survival through activation of a tyrosine kinase.
What is the definition of blood involvement in sezary syndrome?
- Presence of an absolute Sézary cell count of greater than 1000/µL,
- CD4:CD8 ratio greater than or equal to 10 due to CD4 cell expansion
- Loss of one or more T-cell antigens (>30% of T-cells with CD4+/CD7– phenotype or >40% of T cells with a CD4+/CD26–phenotype)
What are the immunophenotypic features of sezary cells?
- CD3+, CD5+ and CD4+, typically without expression of CD7 or CD26.
- PD1+
- Loss of CD2 in ~25% of cases.